Remove support for sqlalchemy-migrate < 0.7

The sqlalchemy-migrate dependency already requires >= 0.7, so supporting
anything older is unnecessary

Change-Id: I0cfd640f420b4fe2837b496f4ef3d3e260619b63
Verify if the RPC result is an instance of dict

The RPC client is currently assuming that all values returned from the
API are iterable. Since errors are always returned as dicts, this patch
verifies whether the returned value is an instance of dict before
checking for the existence of the _error key.

Fixes bug: #1204668

Change-Id: Ie953d7dd2d327334789d66f689a30ce5e36afba9
Merge "Verify if the RPC result is an instance of dict"
Merge "Remove support for sqlalchemy-migrate < 0.7"