Comment 4 for bug 1600281

Reproduce it in standalone (without tripleo):

# neutron-db-manage --config-file /etc/neutron/neutron.conf --config-file /etc/neutron/plugins/ml2/ml2_conf.ini upgrade head
No handlers could be found for logger "oslo_config.cfg"
Traceback (most recent call last):
  File "/bin/neutron-db-manage", line 10, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/neutron/db/migration/cli.py", line 749, in main
    return_val |= bool(CONF.command.func(config, CONF.command.name))
  File "/usr/lib/python2.7/site-packages/neutron/db/migration/cli.py", line 223, in do_upgrade
    run_sanity_checks(config, revision)
  File "/usr/lib/python2.7/site-packages/neutron/db/migration/cli.py", line 731, in run_sanity_checks
    script_dir.run_env()
  File "/usr/lib/python2.7/site-packages/alembic/script/base.py", line 397, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/usr/lib/python2.7/site-packages/alembic/util/pyfiles.py", line 81, 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/neutron/db/migration/alembic_migrations/env.py", line 25, in <module>
    from neutron.db.migration.models import head # noqa
  File "/usr/lib/python2.7/site-packages/neutron/db/migration/models/head.py", line 28, in <module>
    from neutron.db import bgp_db # noqa
  File "/usr/lib/python2.7/site-packages/neutron/db/bgp_db.py", line 26, in <module>
    from neutron_lib.api import validators
ImportError: No module named api