Specify raise_on_warnings=False for mysqlconnector

mysqlconnector driver in sqlalchemy <1.0 uses the wrong default value
for raise_on_warnings.  With raise_on_warnings=True, many things we
expect to be warnings become fatal (like DROP DATABASE IF EXISTS
non_existent_db).

See https://bitbucket.org/zzzeek/sqlalchemy/issue/2515 for upstream bug.

Change-Id: Ic29c9bb6c692952640e3948f5ce31290e158068f
oslo.db.api module documentation

Change-Id: Ibd94d9d8e7f2930f55401cf556a41e41198d4be1
Updated from global requirements

Change-Id: Id12176070ac675883a7ad90c8a46c494b592747e
Merge "oslo.db.api module documentation"
Merge "Updated from global requirements"
Merge "Specify raise_on_warnings=False for mysqlconnector"