compatibility with new python-docker

[TomasTomecek]

=================================== FAILURES ===================================
________________________________ test_short_id _________________________________

    def test_short_id():
        mock()
>       b = DockerBackend()

test_container_info.py:8: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <sen.docker_backend.DockerBackend object at 0x7f6c7cbac050>

    def __init__(self):
        self._containers = None
        self._images = None  # displayed images
        self._all_images = None  # docker images -a
        self._df = None

        kwargs = {"version": "auto"}
>       kwargs.update(docker.utils.kwargs_from_env(assert_hostname=False))
E       TypeError: kwargs_from_env() got an unexpected keyword argument 'assert_hostname'

../sen/docker_backend.py:794: TypeError

[7/9] Installing python3-docker-0:7.1.0 100% |  16.3 MiB/s |   1.1 MiB |  00m00s