Clean up all Python 3.6 warnings

Fixed a few Python3.6 deprecation warnings by replacing ``StopIteration``
with ``return``, as well as using ``getfullargspec()`` instead of
``getargspec()`` under Python 3.

Additionally fixed docstrings with backslashes needing r'', filehandles
not explicitly closed, accommodate for .pyc files not necessarily present.

Change-Id: Id9791c5fa8b4b1f3e4e36f237a8a8ebcef4aaaba
Fixes: #458

1 files changed, 2 insertions, 2 deletions

diff --git a/alembic/script/revision.py b/alembic/script/revision.py
index 1e68a7c..3d9a332 100644
--- a/alembic/script/revision.py
+++ b/alembic/script/revision.py
@@ -656,7 +656,7 @@ class RevisionMap(object):
         uppers = util.dedupe_tuple(self.get_revisions(upper))
 
         if not uppers and not requested_lowers:
-            raise StopIteration()
+            return
 
         upper_ancestors = set(self._get_ancestor_nodes(uppers, check=True))
 
@@ -716,7 +716,7 @@ class RevisionMap(object):
             # if the requested start is one of those branch points,
             # then just return empty set
             if start_from.intersection(upper_ancestors):
-                raise StopIteration()
+                return
             else:
                 # otherwise, they requested nodes out of
                 # order