Comment 0 for bug 1681776

When using mongo as backend for panko, db sync fails due missing libraries.
pymongo is needed for source images.

2017-04-11 11:38:17.150 51 CRITICAL panko [-] RetryError: RetryError[<Future at 0x2c238d0 state=finished raised ImportError>]
2017-04-11 11:38:17.150 51 ERROR panko Traceback (most recent call last):
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/bin/panko-dbsync", line 10, in <module>
2017-04-11 11:38:17.150 51 ERROR panko sys.exit(dbsync())
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/panko/cmd/storage.py", line 29, in dbsync
2017-04-11 11:38:17.150 51 ERROR panko storage.get_connection_from_config(conf).upgrade()
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/panko/storage/__init__.py", line 73, in get_connection_from_config
2017-04-11 11:38:17.150 51 ERROR panko return _inner()
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/tenacity/__init__.py", line 86, in wrapped_f
2017-04-11 11:38:17.150 51 ERROR panko return r.call(f, *args, **kw)
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/tenacity/__init__.py", line 234, in call
2017-04-11 11:38:17.150 51 ERROR panko do = self.iter(result=result, exc_info=exc_info)
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/tenacity/__init__.py", line 205, in iter
2017-04-11 11:38:17.150 51 ERROR panko six.raise_from(RetryError(fut), fut.exception())
2017-04-11 11:38:17.150 51 ERROR panko File "/var/lib/kolla/venv/lib/python2.7/site-packages/six.py", line 718, in raise_from
2017-04-11 11:38:17.150 51 ERROR panko raise value
2017-04-11 11:38:17.150 51 ERROR panko RetryError: RetryError[<Future at 0x2c238d0 state=finished raised ImportError>]
2017-04-11 11:38:17.150 51 ERROR panko