ensure single import per line

This adds the very small plugin flake8-import-single which
will prevent us from having an import with more than one symbol
on a line.

Flake8 by itself prevents this pattern with E401:

   import collections, os, sys

However does not do anything with this:

   from sqlalchemy import Column, text

Both statements have the same issues generating merge artifacts
as well as presenting a manual decision to be made.   While
zimports generally cleans up such imports at the top level, we
don't enforce zimports / pre-commit use.

the plugin finds the same issue for imports that are inside of
test methods.   We shouldn't usually have imports in test methods
so most of them here are moved to be top level.

The version is pinned at 0.1.5; the project seems to have no
activity since 2019, however there are three 0.1.6dev releases
on pypi which stopped in September 2019, they seem to be
experiments with packaging.  The source for 0.1.5
is extremely simple and only reveals one method to flake8
(the run() method).

Change-Id: Icea894e43bad9c0b5d4feb5f49c6c666d6ea6aa1

4 files changed, 9 insertions, 11 deletions

diff --git a/tests/test_autogen_render.py b/tests/test_autogen_render.py
index f138df5..ada2a12 100644
--- a/tests/test_autogen_render.py
+++ b/tests/test_autogen_render.py
@@ -25,6 +25,7 @@ from sqlalchemy import text
 from sqlalchemy import types
 from sqlalchemy import Unicode
 from sqlalchemy import UniqueConstraint
+from sqlalchemy import VARCHAR
 from sqlalchemy.engine.default import DefaultDialect
 from sqlalchemy.sql import and_
 from sqlalchemy.sql import column
@@ -1792,7 +1793,6 @@ class AutogenRenderTest(TestBase):
         )
 
     def test_render_variant(self):
-        from sqlalchemy import VARCHAR, CHAR
 
         self.autogen_context.opts["user_module_prefix"] = None
 
@@ -1824,8 +1824,6 @@ class AutogenRenderTest(TestBase):
         )
 
     def test_repr_user_type_user_prefix_present(self):
-        from sqlalchemy.types import UserDefinedType
-
         class MyType(UserDefinedType):
             def get_col_spec(self):
                 return "MYTYPE"
diff --git a/tests/test_op.py b/tests/test_op.py
index 5682abb..c483c4a 100644
--- a/tests/test_op.py
+++ b/tests/test_op.py
@@ -14,10 +14,13 @@ from sqlalchemy import Table
 from sqlalchemy import UniqueConstraint
 from sqlalchemy.sql import column
 from sqlalchemy.sql import func
+from sqlalchemy.sql import table
 from sqlalchemy.sql import text
 from sqlalchemy.sql.schema import quoted_name
 
 from alembic import op
+from alembic.operations import MigrateOperation
+from alembic.operations import Operations
 from alembic.operations import ops
 from alembic.operations import schemaobj
 from alembic.testing import assert_raises_message
@@ -1023,8 +1026,6 @@ class OpTest(TestBase):
 
     def test_inline_literal(self):
         context = op_fixture()
-        from sqlalchemy.sql import table, column
-        from sqlalchemy import String, Integer
 
         account = table(
             "account", column("name", String), column("id", Integer)
@@ -1144,8 +1145,6 @@ class OpTest(TestBase):
 class SQLModeOpTest(TestBase):
     def test_auto_literals(self):
         context = op_fixture(as_sql=True, literal_binds=True)
-        from sqlalchemy.sql import table, column
-        from sqlalchemy import String, Integer
 
         account = table(
             "account", column("name", String), column("id", Integer)
@@ -1179,8 +1178,6 @@ class SQLModeOpTest(TestBase):
 
 class CustomOpTest(TestBase):
     def test_custom_op(self):
-        from alembic.operations import Operations, MigrateOperation
-
         @Operations.register_operation("create_sequence")
         class CreateSequenceOp(MigrateOperation):
             """Create a SEQUENCE."""
diff --git a/tests/test_postgresql.py b/tests/test_postgresql.py
index 6a67e0b..23d6a8c 100644
--- a/tests/test_postgresql.py
+++ b/tests/test_postgresql.py
@@ -19,9 +19,11 @@ from sqlalchemy import types
 from sqlalchemy import UniqueConstraint
 from sqlalchemy.dialects.postgresql import ARRAY
 from sqlalchemy.dialects.postgresql import BYTEA
+from sqlalchemy.dialects.postgresql import ExcludeConstraint
 from sqlalchemy.dialects.postgresql import HSTORE
 from sqlalchemy.dialects.postgresql import JSON
 from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.dialects.postgresql import TSRANGE
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.sql import column
 from sqlalchemy.sql import false
@@ -1248,7 +1250,6 @@ class PGUniqueIndexAutogenerateTest(AutogenFixtureTest, TestBase):
 
     @config.requirements.btree_gist
     def test_exclude_const_unchanged(self):
-        from sqlalchemy.dialects.postgresql import TSRANGE, ExcludeConstraint
 
         m1 = MetaData()
         m2 = MetaData()
diff --git a/tests/test_script_production.py b/tests/test_script_production.py
index bedf545..5c4cd9e 100644
--- a/tests/test_script_production.py
+++ b/tests/test_script_production.py
@@ -5,7 +5,10 @@ from unittest.mock import patch
 
 from dateutil import tz
 import sqlalchemy as sa
+from sqlalchemy import Column
 from sqlalchemy import inspect
+from sqlalchemy import MetaData
+from sqlalchemy import Table
 
 from alembic import autogenerate
 from alembic import command
@@ -717,7 +720,6 @@ class ImportsTest(TestBase):
         )
 
     def test_imports_in_script(self):
-        from sqlalchemy import MetaData, Table, Column
         from sqlalchemy.dialects.mysql import VARCHAR
 
         type_ = VARCHAR(20, charset="utf8", national=True)