Resolve the following error when logging into the remote docker registry.
Failed to import the required Python library (Docker SDK for Python:
docker (Python >= 2.7) or docker-py (Python 2.6)) on
ubuntu-bionic-rax-dfw-0015461365's Python /usr/bin/python3.
Please read module documentation and install in the appropriate
location, for example via `pip install docker` or `pip install docker-py`
(Python 2.6). The error was: No module named 'docker'
Change-Id: I0df7e58aae886dfa3901815a60853e47c98b5e90
ef33f672a3