[Backend Dependencies Update] Update alembic to 1.3.2

[pyup-bot]

This PR updates alembic from 1.2.1 to 1.3.2.

Changelog

1.3.2

:released: December 16, 2019

 .. change::
     :tags: bug, api, autogenerate
     :tickets: 635

     Fixed regression introduced by :ticket:`579` where server default rendering
     functions began to require a dialect implementation, however the
     :func:`.render_python_code` convenience function did not include one, thus
     causing the function to fail when used in a server default context.  The
     function now accepts a migration context argument and also creates one
     against the default dialect if one is not provided.


.. changelog::

1.3.1

:released: November 13, 2019

 .. change::
     :tags: bug, mssql
     :tickets: 621

     Fixed bug in MSSQL dialect where the drop constraint execution steps used
     to remove server default or implicit foreign key constraint failed to take
     into account the schema name of the target table.


.. changelog::

1.3.0

:released: October 31, 2019

 .. change::
     :tags: feature, command
     :tickets: 608

     Added support for ALEMBIC_CONFIG environment variable,
     refers to the location of the alembic configuration script
     in lieu of using the -c command line option.


 .. change::
     :tags: bug, autogenerate
     :tickets: 131

     Fixed bug in new Variant autogenerate where the order of the arguments to
     Variant were mistakenly reversed.

 .. change::
     :tags: change, compatibility

     Some internal modifications have been made to how the names of indexes and
     unique constraints work to make use of new functions added in SQLAlchemy
     1.4, so that SQLAlchemy has more flexibility over how naming conventions
     may be applied to these objects.

.. changelog::

Links

• PyPI: https://pypi.org/project/alembic
• Changelog: https://pyup.io/changelogs/alembic/
• Homepage: https://alembic.sqlalchemy.org
• Docs: https://pythonhosted.org/alembic/

[pyup-bot]

Closing this in favor of #795