Devstack job fails on backup tests

Global requirements for cassandra-driver is >=2.1.4, however our requirements are ==2.1.3. Devstack in jenkins installs cassandra-driver==2.5.1 and fails on tests with backups with this error on server side:

  File "/usr/local/lib/python2.7/dist-packages/pecan/templating.py", line 23, in render
    return encode(namespace)
  File "/usr/local/lib/python2.7/dist-packages/pecan/jsonify.py", line 137, in encode
    return _instance.encode(obj)
  File "/usr/local/lib/python2.7/dist-packages/simplejson/encoder.py", line 270, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/local/lib/python2.7/dist-packages/simplejson/encoder.py", line 352, in iterencode
    return _iterencode(o, 0)
  File "/usr/local/lib/python2.7/dist-packages/pecan/jsonify.py", line 131, in default
    return jsonify(obj)
  File "/usr/local/lib/python2.7/dist-packages/singledispatch.py", line 210, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
  File "/usr/local/lib/python2.7/dist-packages/pecan/jsonify.py", line 126, in jsonify
    return _default.default(obj)
  File "/usr/local/lib/python2.7/dist-packages/pecan/jsonify.py", line 112, in default
    return JSONEncoder.default(self, obj)
  File "/usr/local/lib/python2.7/dist-packages/simplejson/encoder.py", line 247, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: OrderedMapSerializedKey([(u'name', u'default')]) is not JSON serializable