Resolving issue #210 deprecation warning in python 3.7

*When this change indeed resolves your problem, please **Close** this issue*.
*(You can do so usingthe WorkFlow pull-down (close to the top right of this page)*

27 files changed, 244 insertions, 163 deletions

diff --git a/_test/roundtrip.py b/_test/roundtrip.py
index 0037437..3a842a9 100644
--- a/_test/roundtrip.py
+++ b/_test/roundtrip.py
@@ -1,3 +1,4 @@
+# coding: utf-8
 
 from __future__ import print_function
 
@@ -7,9 +8,6 @@ helper routines for testing round trip of commented YAML data
 import sys
 import textwrap
 
-import ruamel.yaml
-from ruamel.yaml.compat import StringIO, BytesIO  # NOQA
-
 
 def dedent(data):
     try:
@@ -25,6 +23,7 @@ def dedent(data):
 
 
 def round_trip_load(inp, preserve_quotes=None, version=None):
+    import ruamel.yaml  # NOQA
     dinp = dedent(inp)
     return ruamel.yaml.load(
         dinp,
@@ -35,6 +34,7 @@ def round_trip_load(inp, preserve_quotes=None, version=None):
 
 
 def round_trip_load_all(inp, preserve_quotes=None, version=None):
+    import ruamel.yaml  # NOQA
     dinp = dedent(inp)
     return ruamel.yaml.load_all(
         dinp,
@@ -47,6 +47,7 @@ def round_trip_load_all(inp, preserve_quotes=None, version=None):
 def round_trip_dump(data, stream=None,
                     indent=None, block_seq_indent=None, top_level_colon_align=None,
                     prefix_colon=None, explicit_start=None, explicit_end=None, version=None):
+    import ruamel.yaml  # NOQA
     return ruamel.yaml.round_trip_dump(data, stream=stream,
                                        indent=indent, block_seq_indent=block_seq_indent,
                                        top_level_colon_align=top_level_colon_align,
@@ -111,52 +112,59 @@ def round_trip(inp, outp=None, extra=None, intermediate=None, indent=None,
     return data
 
 
-class YAML(ruamel.yaml.YAML):
-    """auto dedent string parameters on load"""
-    def load(self, stream):
-        if isinstance(stream, str):
-            if stream and stream[0] == '\n':
-                stream = stream[1:]
-            stream = textwrap.dedent(stream)
-        return ruamel.yaml.YAML.load(self, stream)
-
-    def load_all(self, stream):
-        if isinstance(stream, str):
+def YAML(**kw):
+    import ruamel.yaml  # NOQA
+
+    class MyYAML(ruamel.yaml.YAML):
+        """auto dedent string parameters on load"""
+        def load(self, stream):
+            if isinstance(stream, str):
+                if stream and stream[0] == '\n':
+                    stream = stream[1:]
+                stream = textwrap.dedent(stream)
+            return ruamel.yaml.YAML.load(self, stream)
+
+        def load_all(self, stream):
+            if isinstance(stream, str):
+                if stream and stream[0] == '\n':
+                    stream = stream[1:]
+                stream = textwrap.dedent(stream)
+            for d in ruamel.yaml.YAML.load_all(self, stream):
+                yield d
+
+        def dump(self, data, **kw):
+            from ruamel.yaml.compat import StringIO, BytesIO  # NOQA
+            assert ('stream' in kw) ^ ('compare' in kw)
+            if 'stream' in kw:
+                return ruamel.yaml.YAML.dump(data, **kw)
+            lkw = kw.copy()
+            expected = textwrap.dedent(lkw.pop('compare'))
+            unordered_lines = lkw.pop('unordered_lines', False)
+            if expected and expected[0] == '\n':
+                expected = expected[1:]
+            lkw['stream'] = st = StringIO()
+            ruamel.yaml.YAML.dump(self, data, **lkw)
+            res = st.getvalue()
+            print(res)
+            if unordered_lines:
+                res = sorted(res.splitlines())
+                expected = sorted(expected.splitlines())
+            assert res == expected
+
+        def round_trip(self, stream, **kw):
+            from ruamel.yaml.compat import StringIO, BytesIO  # NOQA
+            assert isinstance(stream, ruamel.yaml.compat.text_type)
+            lkw = kw.copy()
             if stream and stream[0] == '\n':
                 stream = stream[1:]
             stream = textwrap.dedent(stream)
-        for d in ruamel.yaml.YAML.load_all(self, stream):
-            yield d
-
-    def dump(self, data, **kw):
-        assert ('stream' in kw) ^ ('compare' in kw)
-        if 'stream' in kw:
-            return ruamel.yaml.YAML.dump(data, **kw)
-        lkw = kw.copy()
-        expected = textwrap.dedent(lkw.pop('compare'))
-        unordered_lines = lkw.pop('unordered_lines', False)
-        if expected and expected[0] == '\n':
-            expected = expected[1:]
-        lkw['stream'] = st = StringIO()
-        ruamel.yaml.YAML.dump(self, data, **lkw)
-        res = st.getvalue()
-        print(res)
-        if unordered_lines:
-            res = sorted(res.splitlines())
-            expected = sorted(expected.splitlines())
-        assert res == expected
-
-    def round_trip(self, stream, **kw):
-        assert isinstance(stream, ruamel.yaml.compat.text_type)
-        lkw = kw.copy()
-        if stream and stream[0] == '\n':
-            stream = stream[1:]
-        stream = textwrap.dedent(stream)
-        data = ruamel.yaml.YAML.load(self, stream)
-        outp = lkw.pop('outp', stream)
-        lkw['stream'] = st = StringIO()
-        ruamel.yaml.YAML.dump(self, data, **lkw)
-        res = st.getvalue()
-        if res != outp:
-            diff(outp, res, "input string")
-        assert res == outp
+            data = ruamel.yaml.YAML.load(self, stream)
+            outp = lkw.pop('outp', stream)
+            lkw['stream'] = st = StringIO()
+            ruamel.yaml.YAML.dump(self, data, **lkw)
+            res = st.getvalue()
+            if res != outp:
+                diff(outp, res, "input string")
+            assert res == outp
+
+    return MyYAML(**kw)
diff --git a/_test/test_add_xxx.py b/_test/test_add_xxx.py
index 5b064f7..f2e976f 100644
--- a/_test/test_add_xxx.py
+++ b/_test/test_add_xxx.py
@@ -2,9 +2,8 @@
 
 import re
 import pytest   # NOQA
-import ruamel.yaml
 
-from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
+from roundtrip import dedent
 
 
 # from PyYAML docs
@@ -27,18 +26,21 @@ def dice_representer(dumper, data):
 
 
 def test_dice_constructor():
+    import ruamel.yaml  # NOQA
     ruamel.yaml.add_constructor(u'!dice', dice_constructor)
     data = ruamel.yaml.load('initial hit points: !dice 8d4', Loader=ruamel.yaml.Loader)
     assert str(data) == "{'initial hit points': Dice(8,4)}"
 
 
 def test_dice_constructor_with_loader():
+    import ruamel.yaml  # NOQA
     ruamel.yaml.add_constructor(u'!dice', dice_constructor, Loader=ruamel.yaml.Loader)
     data = ruamel.yaml.load('initial hit points: !dice 8d4', Loader=ruamel.yaml.Loader)
     assert str(data) == "{'initial hit points': Dice(8,4)}"
 
 
 def test_dice_representer():
+    import ruamel.yaml  # NOQA
     ruamel.yaml.add_representer(Dice, dice_representer)
     # ruamel.yaml 0.15.8+ no longer forces quotes tagged scalars
     assert ruamel.yaml.dump(dict(gold=Dice(10, 6)), default_flow_style=False) == \
@@ -46,6 +48,7 @@ def test_dice_representer():
 
 
 def test_dice_implicit_resolver():
+    import ruamel.yaml  # NOQA
     pattern = re.compile(r'^\d+d\d+$')
     ruamel.yaml.add_implicit_resolver(u'!dice', pattern)
     assert ruamel.yaml.dump(dict(treasure=Dice(10, 20)), default_flow_style=False) == \
@@ -74,6 +77,7 @@ class YAMLObj1(object):
 
     @classmethod
     def from_yaml(cls, loader, suffix, node):
+        import ruamel.yaml  # NOQA
         obj1 = Obj1(suffix)
         if isinstance(node, ruamel.yaml.MappingNode):
             obj1.add_node(loader.construct_mapping(node))
@@ -87,6 +91,7 @@ class YAMLObj1(object):
 
 
 def test_yaml_obj():
+    import ruamel.yaml  # NOQA
     ruamel.yaml.add_representer(Obj1, YAMLObj1.to_yaml)
     ruamel.yaml.add_multi_constructor(YAMLObj1.yaml_tag, YAMLObj1.from_yaml)
     x = ruamel.yaml.load('!obj:x.2\na: 1', Loader=ruamel.yaml.Loader)
@@ -95,6 +100,7 @@ def test_yaml_obj():
 
 
 def test_yaml_obj_with_loader_and_dumper():
+    import ruamel.yaml  # NOQA
     ruamel.yaml.add_representer(Obj1, YAMLObj1.to_yaml, Dumper=ruamel.yaml.Dumper)
     ruamel.yaml.add_multi_constructor(YAMLObj1.yaml_tag, YAMLObj1.from_yaml,
                                       Loader=ruamel.yaml.Loader)
@@ -109,28 +115,30 @@ def test_yaml_obj_with_loader_and_dumper():
 
 # Issue 127 reported by Tommy Wang
 
-class Ref(ruamel.yaml.YAMLObject):
-    yaml_constructor = ruamel.yaml.RoundTripConstructor
-    yaml_representer = ruamel.yaml.RoundTripRepresenter
-    yaml_tag = u'!Ref'
 
-    def __init__(self, logical_id):
-        self.logical_id = logical_id
+def test_issue_127():
+    import ruamel.yaml  # NOQA
 
-    @classmethod
-    def from_yaml(cls, loader, node):
-        return cls(loader.construct_scalar(node))
+    class Ref(ruamel.yaml.YAMLObject):
+        yaml_constructor = ruamel.yaml.RoundTripConstructor
+        yaml_representer = ruamel.yaml.RoundTripRepresenter
+        yaml_tag = u'!Ref'
 
-    @classmethod
-    def to_yaml(cls, dumper, data):
-        if isinstance(data.logical_id, ruamel.yaml.scalarstring.ScalarString):
-            style = data.logical_id.style   # ruamel.yaml>0.15.8
-        else:
-            style = None
-        return dumper.represent_scalar(cls.yaml_tag, data.logical_id, style=style)
+        def __init__(self, logical_id):
+            self.logical_id = logical_id
 
+        @classmethod
+        def from_yaml(cls, loader, node):
+            return cls(loader.construct_scalar(node))
+
+        @classmethod
+        def to_yaml(cls, dumper, data):
+            if isinstance(data.logical_id, ruamel.yaml.scalarstring.ScalarString):
+                style = data.logical_id.style   # ruamel.yaml>0.15.8
+            else:
+                style = None
+            return dumper.represent_scalar(cls.yaml_tag, data.logical_id, style=style)
 
-def test_issue_127():
     document = dedent('''\
     AList:
       - !Ref One
diff --git a/_test/test_anchor.py b/_test/test_anchor.py
index 8b83c3e..ae6469a 100644
--- a/_test/test_anchor.py
+++ b/_test/test_anchor.py
@@ -9,9 +9,6 @@ from textwrap import dedent
 import platform
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
-from ruamel.yaml.compat import PY3
-from ruamel.yaml.error import ReusedAnchorWarning
-from ruamel.yaml import version_info
 
 
 def load(s):
@@ -233,6 +230,7 @@ class TestAnchorsAliases:
 
     # this is an error in PyYAML
     def test_reused_anchor(self):
+        from ruamel.yaml.error import ReusedAnchorWarning
         yaml = '''
         - &a
           x: 1
@@ -354,6 +352,7 @@ class TestMergeKeysValues:
 
     def test_len_items_delete(self):
         from ruamel.yaml import safe_load
+        from ruamel.yaml.compat import PY3
         d = safe_load(self.yaml_str)
         data = round_trip_load(self.yaml_str)
         x = data[2].items()
@@ -375,6 +374,7 @@ class TestMergeKeysValues:
 
 class TestDuplicateKeyThroughAnchor:
     def test_duplicate_key_00(self):
+        from ruamel.yaml import version_info
         from ruamel.yaml import safe_load, round_trip_load
         from ruamel.yaml.constructor import DuplicateKeyFutureWarning, DuplicateKeyError
         s = dedent("""\
diff --git a/_test/test_api_change.py b/_test/test_api_change.py
index 65789f4..59473fe 100644
--- a/_test/test_api_change.py
+++ b/_test/test_api_change.py
@@ -9,31 +9,35 @@ testing of anchors and the aliases referring to them
 import sys
 import textwrap
 import pytest
-from ruamel.yaml import YAML, safe_load
-from ruamel.yaml.constructor import DuplicateKeyError, DuplicateKeyFutureWarning
 from ruamel.std.pathlib import Path
 
 
 class TestNewAPI:
     def test_duplicate_keys_00(self):
+        from ruamel.yaml import YAML
         from ruamel.yaml.constructor import DuplicateKeyError
         yaml = YAML()
         with pytest.raises(DuplicateKeyError):
             yaml.load('{a: 1, a: 2}')
 
     def test_duplicate_keys_01(self):
+        from ruamel.yaml import YAML
+        from ruamel.yaml.constructor import DuplicateKeyError
         yaml = YAML(typ='safe', pure=True)
         with pytest.raises(DuplicateKeyError):
             yaml.load('{a: 1, a: 2}')
 
     # @pytest.mark.xfail(strict=True)
     def test_duplicate_keys_02(self):
+        from ruamel.yaml import YAML
+        from ruamel.yaml.constructor import DuplicateKeyError
         yaml = YAML(typ='safe')
         with pytest.raises(DuplicateKeyError):
             yaml.load('{a: 1, a: 2}')
 
     def test_issue_135(self):
         # reported by Andrzej Ostrowski
+        from ruamel.yaml import YAML
         data = {'a': 1, 'b': 2}
         yaml = YAML(typ='safe')
         # originally on 2.7: with pytest.raises(TypeError):
@@ -41,6 +45,7 @@ class TestNewAPI:
 
     def test_issue_135_temporary_workaround(self):
         # never raised error
+        from ruamel.yaml import YAML
         data = {'a': 1, 'b': 2}
         yaml = YAML(typ='safe', pure=True)
         yaml.dump(data, sys.stdout)
@@ -48,6 +53,7 @@ class TestNewAPI:
 
 class TestWrite:
     def test_dump_path(self, tmpdir):
+        from ruamel.yaml import YAML
         fn = Path(str(tmpdir)) / 'test.yaml'
         yaml = YAML()
         data = yaml.map()
@@ -57,6 +63,7 @@ class TestWrite:
         assert fn.read_text() == "a: 1\nb: 2\n"
 
     def test_dump_file(self, tmpdir):
+        from ruamel.yaml import YAML
         fn = Path(str(tmpdir)) / 'test.yaml'
         yaml = YAML()
         data = yaml.map()
@@ -67,6 +74,7 @@ class TestWrite:
         assert fn.read_text() == "a: 1\nb: 2\n"
 
     def test_dump_missing_stream(self):
+        from ruamel.yaml import YAML
         yaml = YAML()
         data = yaml.map()
         data['a'] = 1
@@ -75,6 +83,7 @@ class TestWrite:
             yaml.dump(data)
 
     def test_dump_too_many_args(self, tmpdir):
+        from ruamel.yaml import YAML
         fn = Path(str(tmpdir)) / 'test.yaml'
         yaml = YAML()
         data = yaml.map()
@@ -84,6 +93,8 @@ class TestWrite:
             yaml.dump(data, fn, True)
 
     def test_transform(self, tmpdir):
+        from ruamel.yaml import YAML
+
         def tr(s):
             return s.replace(' ', '  ')
 
@@ -96,6 +107,7 @@ class TestWrite:
         assert fn.read_text() == "a:  1\nb:  2\n"
 
     def test_print(self, capsys):
+        from ruamel.yaml import YAML
         yaml = YAML()
         data = yaml.map()
         data['a'] = 1
@@ -108,6 +120,7 @@ class TestWrite:
 class TestRead:
     def test_multi_load(self):
         # make sure reader, scanner, parser get reset
+        from ruamel.yaml import YAML
         yaml = YAML()
         yaml.load('a: 1')
         yaml.load('a: 1')  # did not work in 0.15.4
@@ -116,6 +129,7 @@ class TestRead:
 class TestLoadAll:
     def test_multi_document_load(self, tmpdir):
         """this went wrong on 3.7 because of StopIteration, PR 37 and Issue 211"""
+        from ruamel.yaml import YAML
         fn = Path(str(tmpdir)) / 'test.yaml'
         fn.write_text(textwrap.dedent(u"""\
         ---
@@ -131,6 +145,8 @@ class TestLoadAll:
 class TestDuplSet:
     def test_dupl_set_00(self):
         # round-trip-loader should except
+        from ruamel.yaml import YAML
+        from ruamel.yaml.constructor import DuplicateKeyError
         yaml = YAML()
         with pytest.raises(DuplicateKeyError):
             yaml.load(textwrap.dedent("""\
@@ -146,6 +162,7 @@ class TestDumpLoadUnicode:
     # test triggered by SamH on stackoverflow (https://stackoverflow.com/q/45281596/1307905)
     # and answer by randomir (https://stackoverflow.com/a/45281922/1307905)
     def test_write_unicode(self, tmpdir):
+        from ruamel.yaml import YAML
         yaml = YAML()
         text_dict = {"text": u"HELLO_WORLD©"}
         file_name = str(tmpdir) + '/tstFile.yaml'
@@ -153,6 +170,7 @@ class TestDumpLoadUnicode:
         assert open(file_name, 'rb').read().decode('utf-8') == u'text: HELLO_WORLD©\n'
 
     def test_read_unicode(self, tmpdir):
+        from ruamel.yaml import YAML
         yaml = YAML()
         file_name = str(tmpdir) + '/tstFile.yaml'
         with open(file_name, 'wb') as fp:
@@ -164,6 +182,7 @@ class TestDumpLoadUnicode:
 class TestFlowStyle:
     def test_flow_style(self, capsys):
         # https://stackoverflow.com/questions/45791712/
+        from ruamel.yaml import YAML
         yaml = YAML()
         yaml.default_flow_style = None
         data = yaml.map()
@@ -179,5 +198,7 @@ class TestOldAPI:
     @pytest.mark.xfail(strict=True)
     def test_duplicate_keys_02(self):
         # Issue 165 unicode keys in error/warning
+        from ruamel.yaml import safe_load
+        from ruamel.yaml.constructor import DuplicateKeyFutureWarning
         with pytest.warns(DuplicateKeyFutureWarning):
             safe_load('type: Doméstica\ntype: International')
diff --git a/_test/test_class_register.py b/_test/test_class_register.py
index cb3d6f0..3da9fb7 100644
--- a/_test/test_class_register.py
+++ b/_test/test_class_register.py
@@ -5,7 +5,6 @@ testing of YAML.register_class and @yaml_object
 """
 
 from roundtrip import YAML
-from ruamel.yaml import yaml_object
 
 
 class User0(object):
@@ -91,36 +90,18 @@ class TestRegisterClass(object):
         yaml.dump(d, compare=ys)
 
 
-yml = YAML()
-
-
-@yaml_object(yml)
-class User2(object):
-    def __init__(self, name, age):
-        self.name = name
-        self.age = age
-
-
-@yaml_object(yml)
-class User3(object):
-    yaml_tag = u'!USER'
-
-    def __init__(self, name, age):
-        self.name = name
-        self.age = age
-
-    @classmethod
-    def to_yaml(cls, representer, node):
-        return representer.represent_scalar(cls.yaml_tag,
-                                            u'{.name}-{.age}'.format(node, node))
+class TestDecorator(object):
 
-    @classmethod
-    def from_yaml(cls, constructor, node):
-        return cls(*node.value.split('-'))
+    def test_decorator_implicit(self):
+        from ruamel.yaml import yaml_object
+        yml = YAML()
 
+        @yaml_object(yml)
+        class User2(object):
+            def __init__(self, name, age):
+                self.name = name
+                self.age = age
 
-class TestDecorator(object):
-    def test_decorator_implicit(self):
         ys = '''
         - !User2
           name: Anthon
@@ -130,6 +111,26 @@ class TestDecorator(object):
         yml.dump(d, compare=ys, unordered_lines=True)
 
     def test_decorator_explicit(self):
+        from ruamel.yaml import yaml_object
+        yml = YAML()
+
+        @yaml_object(yml)
+        class User3(object):
+            yaml_tag = u'!USER'
+
+            def __init__(self, name, age):
+                self.name = name
+                self.age = age
+
+            @classmethod
+            def to_yaml(cls, representer, node):
+                return representer.represent_scalar(cls.yaml_tag,
+                                                    u'{.name}-{.age}'.format(node, node))
+
+            @classmethod
+            def from_yaml(cls, constructor, node):
+                return cls(*node.value.split('-'))
+
         ys = '''
         - !USER Anthon-18
         '''
diff --git a/_test/test_collections.py b/_test/test_collections.py
index 638dde5..e70dbd2 100644
--- a/_test/test_collections.py
+++ b/_test/test_collections.py
@@ -8,8 +8,6 @@ This is now so integrated in Python that it can be mapped to !!omap
 """
 
 import pytest    # NOQA
-import ruamel.yaml   # NOQA
-from collections import OrderedDict
 
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
@@ -17,4 +15,6 @@ from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NO
 
 class TestOrderedDict:
     def test_ordereddict(self):
+        from collections import OrderedDict
+        import ruamel.yaml   # NOQA
         assert ruamel.yaml.dump(OrderedDict()) == '!!omap []\n'
diff --git a/_test/test_comments.py b/_test/test_comments.py
index 11e452f..921b193 100644
--- a/_test/test_comments.py
+++ b/_test/test_comments.py
@@ -11,7 +11,7 @@ roundtrip changes
 """
 
 import pytest
-import ruamel.yaml
+import sys
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump
 
@@ -262,6 +262,7 @@ class TestComments:
         """)
 
     def test_dump_utf8(self):
+        import ruamel.yaml  # NOQA
         x = dedent("""\
         ab:
         - x  # comment
@@ -275,6 +276,7 @@ class TestComments:
             assert y == x
 
     def test_dump_unicode_utf8(self):
+        import ruamel.yaml  # NOQA
         x = dedent(u"""\
         ab:
         - x  # comment
@@ -695,8 +697,8 @@ class TestEmptyLines:
 
 
 class TestUnicodeComments:
-    @pytest.mark.skipif(ruamel.yaml.compat.UNICODE_SIZE < 4,
-                        reason="unicode not wide enough")
+
+    @pytest.mark.skipif(sys.version_info < (2, 7), reason="wide unicode")
     def test_issue_55(self):  # reported by Haraguroicha Hsu
         round_trip("""\
         name: TEST
@@ -821,6 +823,7 @@ a: |
 class TestBlockScalarWithComments:
     # issue 99 reported by Colm O'Connor
     def test_scalar_with_comments(self):
+        import ruamel.yaml  # NOQA
         for x in ['', '\n', '\n# Another comment\n', '\n\n', '\n\n# abc\n#xyz\n',
                   '\n\n# abc\n#xyz\n', '# abc\n\n#xyz\n', '\n\n  # abc\n  #xyz\n']:
 
diff --git a/_test/test_copy.py b/_test/test_copy.py
index 37f978d..9a6deb0 100644
--- a/_test/test_copy.py
+++ b/_test/test_copy.py
@@ -7,7 +7,6 @@ Testing copy and deepcopy, instigated by Issue 84 (Peter Amstutz)
 import copy
 
 import pytest            # NOQA
-import ruamel.yaml       # NOQA
 
 from roundtrip import dedent, round_trip_load, round_trip_dump
 
diff --git a/_test/test_datetime.py b/_test/test_datetime.py
index a33d368..b48d529 100644
--- a/_test/test_datetime.py
+++ b/_test/test_datetime.py
@@ -21,7 +21,6 @@ Please note that a fraction can only be included if not equal to 0
 
 import copy
 import pytest    # NOQA
-import ruamel.yaml   # NOQA
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
 
diff --git a/_test/test_documents.py b/_test/test_documents.py
index 7cc1083..6da293a 100644
--- a/_test/test_documents.py
+++ b/_test/test_documents.py
@@ -2,7 +2,6 @@
 
 import pytest   # NOQA
 
-from ruamel import yaml
 from roundtrip import round_trip, round_trip_load_all
 
 
@@ -16,6 +15,7 @@ class TestDocument:
         """, explicit_start=True, explicit_end=True)
 
     def test_multi_doc_begin_end(self):
+        from ruamel import yaml
         docs = list(round_trip_load_all("""\
         ---
         - a
@@ -58,6 +58,7 @@ class TestDocument:
         assert docs == [['a'], ['b']]
 
     def test_multi_doc_ends_only_1_1(self):
+        from ruamel import yaml
         # this is not ok in 1.1
         with pytest.raises(yaml.parser.ParserError):
             docs = list(round_trip_load_all("""\
diff --git a/_test/test_float.py b/_test/test_float.py
index dc39ce9..2bfe098 100644
--- a/_test/test_float.py
+++ b/_test/test_float.py
@@ -5,7 +5,6 @@ from __future__ import print_function, absolute_import, division, unicode_litera
 import pytest  # NOQA
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
-from ruamel.yaml.error import MantissaNoDotYAML1_1Warning
 
 # http://yaml.org/type/int.html is where underscores in integers are defined
 
@@ -146,6 +145,7 @@ class TestFloat:
             assert 3.0517578122e-56 < d < 3.0517578124e-56
 
     def test_yaml_1_1_no_dot(self):
+        from ruamel.yaml.error import MantissaNoDotYAML1_1Warning
         with pytest.warns(MantissaNoDotYAML1_1Warning):
             round_trip_load("""\
             %YAML 1.1
diff --git a/_test/test_flowsequencekey.py b/_test/test_flowsequencekey.py
index 6f6d7db..8490430 100644
--- a/_test/test_flowsequencekey.py
+++ b/_test/test_flowsequencekey.py
@@ -6,7 +6,6 @@ test flow style sequences as keys roundtrip
 """
 
 # import pytest
-# import ruamel.yaml
 
 from roundtrip import round_trip  # , dedent, round_trip_load, round_trip_dump
 
diff --git a/_test/test_indentation.py b/_test/test_indentation.py
index 014f89b..528e3b6 100644
--- a/_test/test_indentation.py
+++ b/_test/test_indentation.py
@@ -7,13 +7,11 @@ from __future__ import unicode_literals
 
 import pytest  # NOQA
 
-import ruamel.yaml
-from ruamel.yaml.util import load_yaml_guess_indent
-
 from roundtrip import round_trip, round_trip_load, round_trip_dump, dedent, YAML
 
 
 def rt(s):
+    import ruamel.yaml
     return ruamel.yaml.dump(
         ruamel.yaml.load(s, Loader=ruamel.yaml.RoundTripLoader),
         Dumper=ruamel.yaml.RoundTripDumper,
@@ -55,6 +53,7 @@ class TestIndent:
 
     # first test by explicitly setting flow style
     def test_added_inline_list(self):
+        import ruamel.yaml
         s1 = dedent("""
         a:
         - b
@@ -72,6 +71,7 @@ class TestIndent:
     # ############ flow mappings
 
     def test_roundtrip_flow_mapping(self):
+        import ruamel.yaml
         s = dedent("""\
         - {a: 1, b: hallo}
         - {j: fka, k: 42}
@@ -209,6 +209,7 @@ class TestYpkgIndent:
 
 
 def guess(s):
+    from ruamel.yaml.util import load_yaml_guess_indent
     x, y, z = load_yaml_guess_indent(dedent(s))
     return y, z
 
diff --git a/_test/test_issues.py b/_test/test_issues.py
index 3260fbf..0e01875 100644
--- a/_test/test_issues.py
+++ b/_test/test_issues.py
@@ -5,13 +5,13 @@ from __future__ import absolute_import, print_function, unicode_literals
 
 import pytest  # NOQA
 
-import ruamel.yaml
 
 from roundtrip import round_trip, round_trip_load, round_trip_dump, dedent  # NOQA
 
 
 class TestIssue61:
     def test_issue_61(self):
+        import ruamel.yaml
         s = dedent("""
         def1: &ANCHOR1
             key1: value1
diff --git a/_test/test_json_numbers.py b/_test/test_json_numbers.py
index b41c350..a580277 100644
--- a/_test/test_json_numbers.py
+++ b/_test/test_json_numbers.py
@@ -4,11 +4,11 @@ from __future__ import print_function
 
 import pytest  # NOQA
 
-import ruamel.yaml
 import json
 
 
 def load(s, typ=float):
+    import ruamel.yaml
     x = '{"low": %s }' % (s)
     print('input: [%s]' % (s), repr(x))
     # just to check it is loadable json
diff --git a/_test/test_none.py b/_test/test_none.py
index ad51109..681f1e0 100644
--- a/_test/test_none.py
+++ b/_test/test_none.py
@@ -2,11 +2,11 @@
 
 
 import pytest    # NOQA
-import ruamel.yaml   # NOQA
 
 
 class TestNone:
     def test_dump00(self):
+        import ruamel.yaml   # NOQA
         data = None
         s = ruamel.yaml.round_trip_dump(data)
         assert s == 'null\n...\n'
@@ -14,6 +14,7 @@ class TestNone:
         assert d == data
 
     def test_dump01(self):
+        import ruamel.yaml   # NOQA
         data = None
         s = ruamel.yaml.round_trip_dump(data, explicit_end=True)
         assert s == 'null\n...\n'
@@ -21,6 +22,7 @@ class TestNone:
         assert d == data
 
     def test_dump02(self):
+        import ruamel.yaml   # NOQA
         data = None
         s = ruamel.yaml.round_trip_dump(data, explicit_end=False)
         assert s == 'null\n...\n'
@@ -28,6 +30,7 @@ class TestNone:
         assert d == data
 
     def test_dump03(self):
+        import ruamel.yaml   # NOQA
         data = None
         s = ruamel.yaml.round_trip_dump(data, explicit_start=True)
         assert s == '---\n...\n'
@@ -35,6 +38,7 @@ class TestNone:
         assert d == data
 
     def test_dump04(self):
+        import ruamel.yaml   # NOQA
         data = None
         s = ruamel.yaml.round_trip_dump(data, explicit_start=True, explicit_end=False)
         assert s == '---\n...\n'
diff --git a/_test/test_numpy.py b/_test/test_numpy.py
index 6a096af..e3a7718 100644
--- a/_test/test_numpy.py
+++ b/_test/test_numpy.py
@@ -7,10 +7,9 @@ try:
 except:  # NOQA
     numpy = None
 
-import ruamel.yaml
-
 
 def Xtest_numpy():
+    import ruamel.yaml
     if numpy is None:
         return
     data = numpy.arange(10)
diff --git a/_test/test_string.py b/_test/test_string.py
index 6b3070f..f095095 100644
--- a/_test/test_string.py
+++ b/_test/test_string.py
@@ -17,7 +17,6 @@ and the chomping modifiers:
 
 import pytest
 import platform
-import ruamel
 
 # from ruamel.yaml.compat import ordereddict
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
@@ -130,6 +129,7 @@ class TestQuotedScalarString:
 class TestReplace:
     """inspired by issue 110 from sandres23"""
     def test_replace_preserved_scalar_string(self):
+        import ruamel
         s = dedent("""\
         foo: |
           foo
@@ -148,6 +148,7 @@ class TestReplace:
         """)
 
     def test_replace_double_quoted_scalar_string(self):
+        import ruamel
         s = dedent("""\
         foo: "foo foo bar foo"
         """)
diff --git a/_test/test_tag.py b/_test/test_tag.py
index 1aba5ab..c4fabc0 100644
--- a/_test/test_tag.py
+++ b/_test/test_tag.py
@@ -2,24 +2,25 @@
 
 import pytest   # NOQA
 
-from ruamel import yaml
 from roundtrip import round_trip, round_trip_load
 
 
-class XXX(yaml.comments.CommentedMap):
-    @staticmethod
-    def yaml_dump(dumper, data):
-        return dumper.represent_mapping(u'!xxx', data)
+def register_xxx(**kw):
+    from ruamel import yaml
 
-    @classmethod
-    def yaml_load(cls, constructor, node):
-        data = cls()
-        yield data
-        constructor.construct_mapping(node, data)
+    class XXX(yaml.comments.CommentedMap):
+        @staticmethod
+        def yaml_dump(dumper, data):
+            return dumper.represent_mapping(u'!xxx', data)
 
+        @classmethod
+        def yaml_load(cls, constructor, node):
+            data = cls()
+            yield data
+            constructor.construct_mapping(node, data)
 
-yaml.add_constructor(u'!xxx', XXX.yaml_load, constructor=yaml.RoundTripConstructor)
-yaml.add_representer(XXX, XXX.yaml_dump, representer=yaml.RoundTripRepresenter)
+    yaml.add_constructor(u'!xxx', XXX.yaml_load, constructor=yaml.RoundTripConstructor)
+    yaml.add_representer(XXX, XXX.yaml_dump, representer=yaml.RoundTripRepresenter)
 
 
 class TestIndentFailures:
@@ -66,6 +67,7 @@ class TestIndentFailures:
 
 class TestRoundTripCustom:
     def test_X1(self):
+        register_xxx()
         round_trip("""\
         !xxx
         name: Anthon
@@ -75,6 +77,7 @@ class TestRoundTripCustom:
 
     @pytest.mark.xfail(strict=True)
     def test_X_pre_tag_comment(self):
+        register_xxx()
         round_trip("""\
         -
           # hello
@@ -86,6 +89,7 @@ class TestRoundTripCustom:
 
     @pytest.mark.xfail(strict=True)
     def test_X_post_tag_comment(self):
+        register_xxx()
         round_trip("""\
         - !xxx
           # hello
diff --git a/_test/test_version.py b/_test/test_version.py
index 4aad308..0855a5c 100644
--- a/_test/test_version.py
+++ b/_test/test_version.py
@@ -2,11 +2,11 @@
 
 import pytest                        # NOQA
 
-import ruamel.yaml
 from roundtrip import dedent, round_trip, round_trip_load
 
 
 def load(s, version=None):
+    import ruamel.yaml  # NOQA
     return ruamel.yaml.round_trip_load(dedent(s), version)
 
 
@@ -111,6 +111,7 @@ class TestVersions:
 class TestIssue62:
     # bitbucket issue 62, issue_62
     def test_00(self):
+        import ruamel.yaml  # NOQA
         s = dedent("""\
         {}# Outside flow collection:
         - ::vector
@@ -126,6 +127,7 @@ class TestIssue62:
         round_trip(s.format(''), preserve_quotes=True)
 
     def test_00_single_comment(self):
+        import ruamel.yaml  # NOQA
         s = dedent("""\
         {}# Outside flow collection:
         - ::vector
@@ -141,6 +143,7 @@ class TestIssue62:
         # round_trip(s.format('%YAML 1.2\n---\n'), preserve_quotes=True, version=(1, 2))
 
     def test_01(self):
+        import ruamel.yaml  # NOQA
         s = dedent("""\
         {}[random plain value that contains a ? character]
         """)
diff --git a/_test/test_yamlfile.py b/_test/test_yamlfile.py
index e7e31ca..d1ba63c 100644
--- a/_test/test_yamlfile.py
+++ b/_test/test_yamlfile.py
@@ -9,8 +9,6 @@ import sys
 import pytest      # NOQA
 import platform
 
-import ruamel.yaml
-from ruamel.yaml.compat import ordereddict
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
 
 
@@ -23,6 +21,8 @@ class TestYAML:
 
     def test_omap_out(self):
         # ordereddict mapped to !!omap
+        from ruamel.yaml.compat import ordereddict
+        import ruamel.yaml  # NOQA
         x = ordereddict([('a', 1), ('b', 2)])
         res = ruamel.yaml.dump(x, default_flow_style=False)
         assert res == dedent("""
@@ -43,6 +43,7 @@ class TestYAML:
     @pytest.mark.skipif(sys.version_info < (2, 7), reason="collections not available")
     def test_dump_collections_ordereddict(self):
         from collections import OrderedDict
+        import ruamel.yaml  # NOQA
         # OrderedDict mapped to !!omap
         x = OrderedDict([('a', 1), ('b', 2)])
         res = ruamel.yaml.dump(x,
@@ -59,6 +60,7 @@ class TestYAML:
                         reason="ruamel.yaml not available")
     def test_dump_ruamel_ordereddict(self):
         from ruamel.ordereddict import ordereddict
+        import ruamel.yaml  # NOQA
         # OrderedDict mapped to !!omap
         x = ordereddict([('a', 1), ('b', 2)])
         res = ruamel.yaml.dump(x,
@@ -83,7 +85,7 @@ class TestYAML:
 
     def test_set_out(self):
         # preferable would be the shorter format without the ': null'
-        # from ruamel.yaml.compat import ordereddict
+        import ruamel.yaml  # NOQA
         x = set(['a', 'b', 'c'])
         res = ruamel.yaml.dump(x, default_flow_style=False)
         assert res == dedent("""
@@ -194,6 +196,7 @@ class TestYAML:
         assert d['c'][1].split('line.')[1] == ''
 
     def test_load_all_perserve_quotes(self):
+        import ruamel.yaml  # NOQA
         s = dedent("""\
         a: 'hello'
         ---
diff --git a/_test/test_yamlobject.py b/_test/test_yamlobject.py
index a5e06d8..ee39c89 100644
--- a/_test/test_yamlobject.py
+++ b/_test/test_yamlobject.py
@@ -1,26 +1,30 @@
 # coding: utf-8
 
 import pytest   # NOQA
-import ruamel.yaml
 
 from roundtrip import round_trip, dedent, round_trip_load, round_trip_dump  # NOQA
 
 
-class Monster(ruamel.yaml.YAMLObject):
-    yaml_tag = u'!Monster'
+def register_monster():
+    import ruamel.yaml  # NOQA
 
-    def __init__(self, name, hp, ac, attacks):
-        self.name = name
-        self.hp = hp
-        self.ac = ac
-        self.attacks = attacks
+    class Monster(ruamel.yaml.YAMLObject):
+        yaml_tag = u'!Monster'
 
-    def __repr__(self):
-        return "%s(name=%r, hp=%r, ac=%r, attacks=%r)" % (
-            self.__class__.__name__, self.name, self.hp, self.ac, self.attacks)
+        def __init__(self, name, hp, ac, attacks):
+            self.name = name
+            self.hp = hp
+            self.ac = ac
+            self.attacks = attacks
+
+        def __repr__(self):
+            return "%s(name=%r, hp=%r, ac=%r, attacks=%r)" % (
+                self.__class__.__name__, self.name, self.hp, self.ac, self.attacks)
 
 
 def test_monster():
+    import ruamel.yaml  # NOQA
+    register_monster()
     data = ruamel.yaml.load(dedent("""\
     --- !Monster
     name: Cave spider
diff --git a/_test/test_z_data.py b/_test/test_z_data.py
index d85ba28..9ea921b 100644
--- a/_test/test_z_data.py
+++ b/_test/test_z_data.py
@@ -9,16 +9,14 @@ import platform  # NOQA
 
 sys.path.insert(0, os.path.dirname(__file__) + '/lib')
 
-import ruamel.yaml     # NOQA
-import test_appliance  # NOQA
 import warnings        # NOQA
-warnings.simplefilter('ignore', ruamel.yaml.error.UnsafeLoaderWarning)
 
 
 args = []
 
 
 def test_data():
+    import test_appliance  # NOQA
     collections = []
     import test_yaml
     collections.append(test_yaml)
@@ -30,6 +28,9 @@ def test_data():
 
 def test_data_ext():
     collections = []
+    import ruamel.yaml     # NOQA
+    import test_appliance  # NOQA
+    warnings.simplefilter('ignore', ruamel.yaml.error.UnsafeLoaderWarning)
     if ruamel.yaml.__with_libyaml__:
         import test_yaml_ext
         collections.append(test_yaml_ext)
diff --git a/comments.py b/comments.py
index afbcbf0..98c80c7 100644
--- a/comments.py
+++ b/comments.py
@@ -11,11 +11,15 @@ a separate base
 import sys
 import copy
 
-from collections import MutableSet, Sized, Set
 
 from ruamel.yaml.compat import ordereddict, PY2, string_types
 from ruamel.yaml.scalarstring import ScalarString
 
+if PY2:
+    from collections import MutableSet, Sized, Set
+else:
+    from collections.abc import MutableSet, Sized, Set
+
 if False:  # MYPY
     from typing import Any, Dict, Optional, List, Union  # NOQA
 
diff --git a/compat.py b/compat.py
index 022762b..e7ad8db 100644
--- a/compat.py
+++ b/compat.py
@@ -83,6 +83,7 @@ if PY3:
     BytesIO = io.BytesIO
     # have unlimited precision
     no_limit_int = int
+    from collections.abc import Hashable  # NOQA
 
 else:
     string_types = basestring    # NOQA
@@ -99,6 +100,7 @@ else:
     BytesIO = cStringIO.StringIO
     # have unlimited precision
     no_limit_int = long  # NOQA not available on Python 3
+    from collections import Hashable  # NOQA
 
 if False:  # MYPY
     # StreamType = Union[BinaryIO, IO[str], IO[unicode],  StringIO]
diff --git a/constructor.py b/constructor.py
index e5126f4..c752b73 100644
--- a/constructor.py
+++ b/constructor.py
@@ -2,7 +2,6 @@
 
 from __future__ import print_function, absolute_import, division
 
-import collections
 import datetime
 import base64
 import binascii
@@ -16,7 +15,7 @@ from ruamel.yaml.error import (MarkedYAMLError, MarkedYAMLFutureWarning,
 from ruamel.yaml.nodes import *                               # NOQA
 from ruamel.yaml.nodes import (SequenceNode, MappingNode, ScalarNode)
 from ruamel.yaml.compat import (utf8, builtins_module, to_str, PY2, PY3,  # NOQA
-                                ordereddict, text_type, nprint, version_tnf)
+                                ordereddict, text_type, nprint, version_tnf, Hashable)
 from ruamel.yaml.comments import *                               # NOQA
 from ruamel.yaml.comments import (CommentedMap, CommentedOrderedMap, CommentedSet,
                                   CommentedKeySeq, CommentedSeq, TaggedScalar)
@@ -217,7 +216,7 @@ class BaseConstructor(object):
                 # keys can be list -> deep
                 key = self.construct_object(key_node, deep=True)
                 # lists are not hashable, but tuples are
-                if not isinstance(key, collections.Hashable):
+                if not isinstance(key, Hashable):
                     if isinstance(key, list):
                         key = tuple(key)
                 if PY2:
@@ -229,7 +228,7 @@ class BaseConstructor(object):
                             "found unacceptable key (%s)" %
                             exc, key_node.start_mark)
                 else:
-                    if not isinstance(key, collections.Hashable):
+                    if not isinstance(key, Hashable):
                         raise ConstructorError(
                             "while constructing a mapping", node.start_mark,
                             "found unhashable key", key_node.start_mark)
@@ -1240,7 +1239,7 @@ class RoundTripConstructor(SafeConstructor):
             # keys can be list -> deep
             key = self.construct_object(key_node, deep=True)
             # lists are not hashable, but tuples are
-            if not isinstance(key, collections.Hashable):
+            if not isinstance(key, Hashable):
                 if isinstance(key, list):
                     key_a = CommentedKeySeq(key)
                     if key_node.flow_style is True:
@@ -1258,7 +1257,7 @@ class RoundTripConstructor(SafeConstructor):
                         "found unacceptable key (%s)" %
                         exc, key_node.start_mark)
             else:
-                if not isinstance(key, collections.Hashable):
+                if not isinstance(key, Hashable):
                     raise ConstructorError(
                         "while constructing a mapping", node.start_mark,
                         "found unhashable key", key_node.start_mark)
@@ -1307,7 +1306,7 @@ class RoundTripConstructor(SafeConstructor):
             # keys can be list -> deep
             key = self.construct_object(key_node, deep=True)
             # lists are not hashable, but tuples are
-            if not isinstance(key, collections.Hashable):
+            if not isinstance(key, Hashable):
                 if isinstance(key, list):
                     key = tuple(key)
             if PY2:
@@ -1319,7 +1318,7 @@ class RoundTripConstructor(SafeConstructor):
                         "found unacceptable key (%s)" %
                         exc, key_node.start_mark)
             else:
-                if not isinstance(key, collections.Hashable):
+                if not isinstance(key, Hashable):
                     raise ConstructorError(
                         "while constructing a mapping", node.start_mark,
                         "found unhashable key", key_node.start_mark)
diff --git a/tox.ini b/tox.ini
index 853902e..2f6b704 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,11 +1,10 @@
 [tox]
-# toworkdir = /data1/DATA/tox/ruamel.yaml 
-envlist = cs,py36,py27,py35,py34,pypy,py27m
+toworkdir = /data1/DATA/tox/ruamel.yaml 
+envlist = cs,py37,py27,py36,py35,py34,pypy,py27m
 
 [testenv]
 commands =
-    python -c "import sys, sysconfig; print('%s ucs-%s' % (sys.version.replace('\n', ' '), sysconfig.get_config_var('Py_UNICODE_SIZE')))"
-    /bin/bash -c 'pytest _test/test_*.py'
+    /bin/bash -c 'pytest -ra _test/test_*.py'
 deps =
     pytest
     flake8==2.5.5
@@ -19,6 +18,19 @@ basepython = python3.6
 commands =
     flake8  --exclude .tox,jabsy,jinja2,base,cmd,convert{posargs}
 
+# deprecation warning
+[testenv:dw]
+basepython = python3.7
+commands =
+    /bin/bash -c 'pytest _test/test_a*.py _test/test_z*.py'
+
+# deprecation warning fail
+[testenv:dwf]
+basepython = python3.7
+commands =
+    /bin/sed 's/collections.abc/collections/' -i .tox/dwf/lib/python3.7/site-packages/ruamel/yaml/comments.py
+    /bin/bash -c 'pytest --maxfail=2 _test/test_[a-vz]*.py'
+
 [testenv:pep8]
 basepython = python3.6
 commands =
@@ -28,3 +40,8 @@ commands =
 show-source = True
 max-line-length = 95
 exclude = _test/lib,.hg,.git,.tox,dist,.cache,__pycache__,ruamel.zip2tar.egg-info
+
+[pytest]
+filterwarnings =
+    error::DeprecationWarning
+    error::PendingDeprecationWarning