Unit test fixes

[cfs-pure]

Fix unittests for compatibility between Python 2 and 3.
Fixed a mock for open() in kmip.services.server.server

[codecov-io]

Current coverage is 87.14% (diff: 100%)

Merging #238 into master will not change coverage

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[cfs-pure]

The problems this pull request fixed came up when rebuilding the python-pykmip package from Ubuntu zesty (0.5.0-4) using the v0.6.0 tarball from PyPI. The Debian build uses python-coverage and not tox.

[PeterHamilton]

I'm fine with the six.assertCountEqual and six.assertRaisesRegex changes. Can you provide more info on the mock.patch change with create=True? Was open not found when you were running the tests?

[cfs-pure]

@PeterHamilton the mock was being applied to the kmip.services.server.server class which does not have an open method.

[PeterHamilton]

I think the open issue will be better handled if I just switch to using mock_open. I'll put out a patch for that. Once that's in, you can pull out the mock.patch change and this should be good to go.

[PeterHamilton]

Nevermind, I'm already using mock_open. The right solution is to scrap the code in the try block and just use the right module for Python 3+, builtins.

[PeterHamilton]

See PR #239 for the open mock fix.

[PeterHamilton]

PR #239 has been merged. Once this PR is updated, I'll merge it as well.

[cfs-pure]

Removed my changes to test_server.py because of #239.