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

2 files changed, 16 insertions, 12 deletions

diff --git a/examples/extending_query/filter_public.py b/examples/extending_query/filter_public.py
index a420e9da4..1ac811583 100644
--- a/examples/extending_query/filter_public.py
+++ b/examples/extending_query/filter_public.py
@@ -14,10 +14,18 @@ that should be applied on a per-request basis, etc.
 
 from sqlalchemy import Boolean
 from sqlalchemy import Column
+from sqlalchemy import create_engine
 from sqlalchemy import event
+from sqlalchemy import ForeignKey
+from sqlalchemy import Integer
 from sqlalchemy import orm
+from sqlalchemy import select
+from sqlalchemy import String
 from sqlalchemy import true
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import relationship
 from sqlalchemy.orm import Session
+from sqlalchemy.orm import sessionmaker
 
 
 @event.listens_for(Session, "do_orm_execute")
@@ -58,12 +66,6 @@ class HasPrivate:
 
 if __name__ == "__main__":
 
-    from sqlalchemy import Integer, Column, String, ForeignKey, Boolean
-    from sqlalchemy import select
-    from sqlalchemy import create_engine
-    from sqlalchemy.orm import relationship, sessionmaker
-    from sqlalchemy.ext.declarative import declarative_base
-
     Base = declarative_base()
 
     class User(HasPrivate, Base):
diff --git a/examples/extending_query/temporal_range.py b/examples/extending_query/temporal_range.py
index 01d0eadf8..dc6d8166f 100644
--- a/examples/extending_query/temporal_range.py
+++ b/examples/extending_query/temporal_range.py
@@ -7,8 +7,16 @@ to selected entities.
 import datetime
 
 from sqlalchemy import Column
+from sqlalchemy import create_engine
 from sqlalchemy import DateTime
+from sqlalchemy import ForeignKey
+from sqlalchemy import Integer
 from sqlalchemy import orm
+from sqlalchemy import select
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import relationship
+from sqlalchemy.orm import selectinload
+from sqlalchemy.orm import sessionmaker
 
 
 class HasTemporal:
@@ -29,12 +37,6 @@ def temporal_range(range_lower, range_upper):
 
 if __name__ == "__main__":
 
-    from sqlalchemy import Integer, Column, ForeignKey
-    from sqlalchemy import select
-    from sqlalchemy import create_engine
-    from sqlalchemy.orm import relationship, sessionmaker, selectinload
-    from sqlalchemy.ext.declarative import declarative_base
-
     Base = declarative_base()
 
     class Parent(HasTemporal, Base):