ansible-container Fix compilation error when running under Python 3.4

ISSUE TYPE

Bugfix Pull Request

SUMMARY

This compilation error was the only obstacle I encountered when running ansible-container with Python 3.4, despite having no issues at all with Docker and Ansible standalone. I tested the full build/run/deploy cycle and everything seems to work fine with this fix applied.

Jun 03 '17 19:06 LeHack

Not being a heavy user of Python3 yet, I'm a little confused. I read this in the docs: https://docs.python.org/3/library/http.html#http.HTTPStatus -- by that read, the code as present is correct. Could you help me understand your PR? Thanks!

Jun 03 '17 20:06 j00bar

Correction, this concerns Python 3.4 (but my fix works also with 3.5). Actually regarding Python I'm not much more than a novice. I found this suggestion somewhere on stackoverflow while trying to resolve the issue that popped up during the build process:

$ ansible-container build 
ERROR	Unknown exception	
Traceback (most recent call last):
  File "/home/.../testapp/lib/python3.4/site-packages/container/docker/engine.py", line 23, in <module>
    import httplib as StatusCodes
ImportError: No module named 'httplib'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/.../testapp/lib/python3.4/site-packages/container/cli.py", line 268, in __call__
    getattr(core, u'hostcmd_{}'.format(args.subcommand))(**vars(args))
  File "/home/.../testapp/lib/python3.4/site-packages/container/__init__.py", line 28, in __wrapped__
    return fn(*args, **kwargs)
  File "/home/.../testapp/lib/python3.4/site-packages/container/core.py", line 137, in hostcmd_build
    config['services'], **kwargs)
  File "/home/.../testapp/lib/python3.4/site-packages/container/utils/loader.py", line 16, in load_engine
    package='container')
  File "/home/.../testapp/lib/python3.4/importlib/__init__.py", line 109, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
  File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
  File "<frozen importlib._bootstrap>", line 2226, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 1129, in _exec
  File "<frozen importlib._bootstrap>", line 1471, in exec_module
  File "<frozen importlib._bootstrap>", line 321, in _call_with_frames_removed
  File "/home/.../testapp/lib/python3.4/site-packages/container/docker/engine.py", line 25, in <module>
    from http import HTTPStatus as StatusCodes
ImportError: cannot import name 'HTTPStatus'

Jun 03 '17 21:06 LeHack

I can confirm that the current develop branch is broken on python 3.4. Like https://docs.python.org/3/library/http.html#http.HTTPStatus mentions it is new in 3.5. I don't think the current code is really the best solution since http.client is a different package from the enum HTTPStatus and importing it this way might lead to subtle bugs.

I'm installing 3.5 and 3.6 to check if I can come with a recommendation for a proper fix.

Jul 10 '17 22:07 ekohl

Having looked into it I'd recommend the following:

try:  # Python 3.5+
    from http import HTTPStatus as StatusCodes
except ImportError:
    try:  # Python 3
        from http import client as StatusCodes
    except ImportError:  # Python 2
        import httplib as StatusCodes

Jul 11 '17 20:07 ekohl

@LeHack

Would you mind modifying this to use the method suggested by @ekohl. Once done, I can merge this.

Thank you for your efforts on this, and apologies for not looking at it in quite awhile.