deprecations: Deprecate support for '-py{N}' requirements

This has been marked as deprecated for a long time in the docs but
we've done nothing to indicate this from a code perspective. Fix this.

Change-Id: I916bf16773a2a2cffa3c352d5dba52e3fbc298c2
Fixes-Bug: #431529

3 files changed, 29 insertions, 6 deletions

diff --git a/pbr/packaging.py b/pbr/packaging.py
index 0177437..38b4982 100644
--- a/pbr/packaging.py
+++ b/pbr/packaging.py
@@ -46,6 +46,8 @@ from pbr import testr_command
 from pbr import version
 
 REQUIREMENTS_FILES = ('requirements.txt', 'tools/pip-requires')
+PY_REQUIREMENTS_FILES = [x % sys.version_info[0] for x in (
+    'requirements-py%d.txt', 'tools/pip-requires-py%d')]
 TEST_REQUIREMENTS_FILES = ('test-requirements.txt', 'tools/test-requires')
 
 
@@ -57,9 +59,8 @@ def get_requirements_files():
     # - REQUIREMENTS_FILES with -py2 or -py3 in the name
     #   (e.g. requirements-py3.txt)
     # - REQUIREMENTS_FILES
-    return (list(map(('-py' + str(sys.version_info[0])).join,
-                     map(os.path.splitext, REQUIREMENTS_FILES)))
-            + list(REQUIREMENTS_FILES))
+
+    return PY_REQUIREMENTS_FILES + list(REQUIREMENTS_FILES)
 
 
 def append_text_list(config, key, text_list):
@@ -78,9 +79,20 @@ def _any_existing(file_list):
 
 # Get requirements from the first file that exists
 def get_reqs_from_files(requirements_files):
-    for requirements_file in _any_existing(requirements_files):
+    existing = _any_existing(requirements_files)
+
+    deprecated = [f for f in existing if f in PY_REQUIREMENTS_FILES]
+    if deprecated:
+        warnings.warn('Support for \'-pyN\'-suffixed requirements files is '
+                      'deprecated in pbr 4.0 and will be removed in 5.0. '
+                      'Use environment markers instead. Conflicting files: '
+                      '%r' % deprecated,
+                      DeprecationWarning)
+
+    for requirements_file in existing:
         with open(requirements_file, 'r') as fil:
             return fil.read().split('\n')
+
     return []
 
 
diff --git a/pbr/tests/test_packaging.py b/pbr/tests/test_packaging.py
index 526e12d..da221d7 100644
--- a/pbr/tests/test_packaging.py
+++ b/pbr/tests/test_packaging.py
@@ -549,14 +549,17 @@ class ParseRequirementsTest(base.BaseTestCase):
         result = packaging.parse_requirements([requirements])
         self.assertEqual(['pbr'], result)
 
-    def test_python_version(self):
+    @mock.patch('warnings.warn')
+    def test_python_version(self, mock_warn):
         with open("requirements-py%d.txt" % sys.version_info[0],
                   "w") as fh:
             fh.write("# this is a comment\nfoobar\n# and another one\nfoobaz")
         self.assertEqual(['foobar', 'foobaz'],
                          packaging.parse_requirements())
+        mock_warn.assert_called_once_with(mock.ANY, DeprecationWarning)
 
-    def test_python_version_multiple_options(self):
+    @mock.patch('warnings.warn')
+    def test_python_version_multiple_options(self, mock_warn):
         with open("requirements-py1.txt", "w") as fh:
             fh.write("thisisatrap")
         with open("requirements-py%d.txt" % sys.version_info[0],
@@ -564,6 +567,9 @@ class ParseRequirementsTest(base.BaseTestCase):
             fh.write("# this is a comment\nfoobar\n# and another one\nfoobaz")
         self.assertEqual(['foobar', 'foobaz'],
                          packaging.parse_requirements())
+        # even though we have multiple offending files, this should only be
+        # called once
+        mock_warn.assert_called_once_with(mock.ANY, DeprecationWarning)
 
 
 class ParseRequirementsTestScenarios(base.BaseTestCase):
diff --git a/releasenotes/notes/deprecate-pyN-requirements-364655c38fa5b780.yaml b/releasenotes/notes/deprecate-pyN-requirements-364655c38fa5b780.yaml
new file mode 100644
index 0000000..3ed9bc7
--- /dev/null
+++ b/releasenotes/notes/deprecate-pyN-requirements-364655c38fa5b780.yaml
@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    Support for ``pyN``-suffixed requirement files has been deprecated:
+    environment markers should be used instead.