Description of problem:
when running octavia-db-manage upgrade head in order to build the db, the command line fails and crashes. function trace is printed out.

Version-Release number of selected component (if applicable):


How reproducible:
Installing director with octavia. you'll see the logs by connecting to the controller and run "docker logs octavia_db_sync".

Steps to Reproduce:
1.setup deployed with jenkins job https://rhos-qe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/OSPD-Customized-Deployment-virt/1337/ 
2. connect to the controller with root user
3. type "docker logs octavia_db_sync"

Actual results:
Traceback (most recent call last):
  File "/usr/bin/octavia-db-manage", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/octavia/db/migration/cli.py", line 132, in main
    CONF.command.func(config, CONF.command.name)
  File "/usr/lib/python2.7/site-packages/octavia/db/migration/cli.py", line 62, in do_upgrade
    do_alembic_command(config, cmd, revision, sql=CONF.command.sql)
  File "/usr/lib/python2.7/site-packages/octavia/db/migration/cli.py", line 30, in do_alembic_command
    getattr(alembic_cmd, cmd)(config, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/alembic/command.py", line 174, in upgrade
    script.run_env()
  File "/usr/lib/python2.7/site-packages/alembic/script/base.py", line 407, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/usr/lib/python2.7/site-packages/alembic/util/pyfiles.py", line 93, in load_python_file
    module = load_module_py(module_id, path)
  File "/usr/lib/python2.7/site-packages/alembic/util/compat.py", line 79, in load_module_py
    mod = imp.load_source(module_id, path, fp)
  File "/usr/lib/python2.7/site-packages/octavia/db/migration/alembic_migrations/env.py", line 92, in <module>
    run_migrations_online()
  File "/usr/lib/python2.7/site-packages/octavia/db/migration/alembic_migrations/env.py", line 76, in run_migrations_online
    poolclass=pool.NullPool)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/__init__.py", line 387, in create_engine
    return strategy.create(*args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 52, in create
    plugins = u._instantiate_plugins(kwargs)
AttributeError: 'NoneType' object has no attribute '_instantiate_plugins'


Expected results:
The output should be similar to this -
INFO  [alembic.runtime.migration] Context impl MySQLImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> 35dee79d5865, initial_create
INFO  [alembic.runtime.migration] Running upgrade 35dee79d5865 -> 4c094013699a, update load balancer amphora relationship
INFO  [alembic.runtime.migration] Running upgrade 4c094013699a -> 13500e2e978d, update url and name size
.
.
.
.


Additional info:
In the undercloud machine you can find under /home/stack/overcloud_deploy.sh the overcloud's deployment script.