TrivialFix

Change-Id: I089d9e8b57895d9878bf82d2fac397722fccc083

Starting in SQLAlchemy 1.1, the rules for when "autoincrement=True"
may be set on a column are more strict.  The migrate tests are
testing the alteration of a column from Integer to String
and then regenerating; this means we need to set autoincrement
to False as well.   A related issue in SQLAlchemy 1.1 is
also being fixed (see https://bitbucket.org/zzzeek/sqlalchemy/issues/3835/),
however this fix is not needed in order for the tests to pass here.

Change-Id: Ibd3a75fff13312411df87e17b6e5764865d69728

Currently migrate.versioning.api.upgrade() raises KeyError
instead of sqlalchemy-migrate specific exception if migration
script file is not present in migration repository.

Raised migrate.exception.VersionNotFoundError if the specified
migration script does not exist in the repository. Made
VersionNotFoundError exception class as a subclass of KeyError
in order to avoid breaking existing users looking for KeyError.

Related-Bug: #1546441
Change-Id: I0210d56a6e85f03c44cea027f50863faaf050c1d

On Python 3, some functions like range() don't try to call the __int__()
method to cast an object to integer, but try instead the __index__()
method.

Add an __index__() method to mimick correctly the int type on Python 3.

Change-Id: I8df116d80e201778714a59367600eaef644266ed

Lift the requirements to support SQLAlchemy 1.0.  Two tests
were calling upon revised APIs and required adjustment.

Change-Id: Ic91a91bb3c915027b522eace302f2ed074233294

Under Python 2.6 a setuptools warning is produced when
the migrate runner runs.  Since migrate invokes its own
commandline client from tests in a separate shell, the
fixture we're using to do that must be told not to complain
about this stderr.

Change-Id: Ib5823754d6ffabe954665f2a7529ed0e56591ebf