Use dialect rather than a particular DB API driver

_get_connect_string() is too specific when choosing a DB API driver to be
used. We shouldn't force users to use neither psycopg2 nor MySQLdb as this is
not required for any actions provided by oslo.db. Specify only the dialect to
 be used and let SQLAlchemy choose one of the DB API drivers available.

Closes-Bug: #1256835
Change-Id: I685f9eecc77f2c1f920c83c5da653f3114a83679
Add check_maintainers.py script

check_maintainers.py verifies that all of the files in the
oslo-incubator tree are covered by an entry in MAINTAINERS

Change-Id: I6c77a250ff3a0b537b17052d8da86b5b48a5283f
generator: rename EXTRA_MODULES_FILE to RC_FILE

Tweak how we use this file to make it clear we can use it for things
other than the EXTRA_MODULES env variable.

Change-Id: Icedf643a7959ba7337423a16cb216918f5e95e77
Merge "Use dialect rather than a particular DB API driver"
Generalize base test case into common code

Code in BaseTestCase from openstack/common/test.py and
test/utils.py look similar. To reduce code duplication, base test case
generalized to common.test. Thus it can be reused in other projects.

Co-Authored-By: Ilya Pekelny <ipekelny@mirantis.com>
Change-Id: I60b6b41d2e6cd379616acec92242740b4bb00da1
Move db tests base.py to common code

tests/unit/db/sqlalchemy/base.py moved to
openstack/common/db/sqlalchemy/test_base.py for further reuse in other
projects.

Change-Id: I5cf83a63f148f48ff7c38a1ad4cc714f08e60fd1
Merge "Add check_maintainers.py script"
Merge "generator: rename EXTRA_MODULES_FILE to RC_FILE"
Merge "Generalize base test case into common code"
Merge "Move db tests base.py to common code"