'ImportError: No module named ssl_match_hostname' upon 'import docker' in a Python script

In a script ~/Documents/Scratch/test_import_docker.py with the single statement import docker, I'm getting the following ImportError:

Traceback (most recent call last):
  File "test_import_docker.py", line 1, in <module>
    import docker
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/__init__.py", line 6, in <module>
    from .client import Client, AutoVersionClient, from_env # flake8: noqa
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/client.py", line 11, in <module>
    from . import api
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/api/__init__.py", line 2, in <module>
    from .build import BuildApiMixin
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/api/build.py", line 9, in <module>
    from .. import utils
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/utils/__init__.py", line 2, in <module>
    from .utils import (
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/utils/utils.py", line 19, in <module>
    from .. import tls
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/tls.py", line 5, in <module>
    from .ssladapter import ssladapter
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/ssladapter/__init__.py", line 1, in <module>
    from .ssladapter import SSLAdapter # flake8: noqa
  File "/home/kurt/.local/lib/python2.7/site-packages/docker/ssladapter/ssladapter.py", line 21, in <module>
    from backports.ssl_match_hostname import match_hostname
ImportError: No module named ssl_match_hostname

Strangely, I am able to import docker from iPython:

Python 2.7.12 (default, Nov 19 2016, 06:48:10) 
Type "copyright", "credits" or "license" for more information.

IPython 2.4.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: import docker

In [2]: 

Why is the import not working in the first case?

My Docker version from the command line is:

kurt@kurt-ThinkPad:~$ docker --version
Docker version 1.12.3, build 6b644ec

whereas the version in Python is

In [3]: docker.version
Out[3]: '1.10.3'

Incidentally, I've also created a StackOverflow question about this.

Reproduce the failure with test_import_docker.py using the same Python interpreter, then inspect docker/init.py and docker/ssladapter/ssladapter.py along with the reported package environments. Compare those imports with the working IPython session; done means the environment or dependency discrepancy is identified and the issue has a confirmed resolution or documented cause.