Fixes the auto-generated manage.py

Removes `six` from the locals().copy() so that it won't be templated into
manage.py.  Currently manage.py is mis-templated and is failing.

Change-Id: Ib3b7c7caac998fbaa45c3370547c9b8bf13abe41
Closes-Bug: 171

migrate/versioning/templates/manage/default.py_tmpl

@@ -5,6 +5,7 @@ from migrate.versioning.shell import main
 import six
 _vars = locals().copy()
 del _vars['__template_name__']
+del _vars['six']
 _vars.pop('repository_name', None)
 defaults = ", ".join(["%s='%s'" % var for var in six.iteritems(_vars)])
 }}

migrate/versioning/templates/manage/pylons.py_tmpl

@@ -20,6 +20,7 @@ else:
 import six
 _vars = locals().copy()
 del _vars['__template_name__']
+del _vars['six']
 defaults = ", ".join(["%s='%s'" % var for var in six.iteritems(_vars)])
 }}