Add tox job for db revision creation

Trivial-Fix

Change-Id: Ie87b84ddd546149ca5d9eaf2179c514071c75695

doc/source/devref/database.rst

@@ -52,3 +52,15 @@ Tests
 
 Tests are lacking for the db api layer and for the sqlalchemy driver.
 Failures in the drivers would be detected in other test cases, though.
+
+DB migration revisions
+----------------------
+
+If a DB schema needs to be updated, a new DB migration file needs to be added
+in ``manila/db/migrations/alembic/versions``. To create such a file it's
+possible to use ``manila-manage db revision`` or the corresponding tox command::
+
+   tox -e dbrevision "change_foo_table"
+
+In addition every migration script must be tested. See examples in
+``manila/tests/db/migrations/alembic/migrations_data_checks.py``.

tox.ini

@@ -90,6 +90,10 @@ deps = -r{toxinidir}/requirements.txt
        pylint==0.26.0
 commands = python tools/lintstack.py check
 
+[testenv:dbrevision]
+deps = -r{toxinidir}/requirements.txt
+commands = alembic -c manila/db/migrations/alembic.ini revision -m ""{posargs}
+
 [flake8]
 # Following checks are ignored on purpose:
 ignore =