Switch all mock imports to unittest.mock imports

[mathmauney]

Description

(Description of what the PR does, such as fixes # {issue number})
Takes care of #2261 by switching all mock imports. I've tested on python 3.4.8 and 3.6.7.

How to test

(Description of how to validate or test this PR)
Run start-mycroft.sh unittest, though Travis should take care of this.

Contributor license agreement signed?

CLA [yes] (Whether you have signed a CLA - Contributor Licensing Agreement

[pep8speaks]

Hello @mathmauney! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-08-27 09:00:40 UTC

[devs-mycroft]

Hello, @mathmauney, thank you for helping with the Mycroft project! We welcome everyone
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for Everyone.

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You retain ownership of the code, this is just a license.

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[forslund]

Thanks @mathmauney, looks really good! Seems there are a couple of pep-8 issues still lingering. Could you look at those as well?

Also could remove the mock dependency from test-requirements.txt?

[mathmauney]

Done and done.

[forslund]

I've rebased the branch and squashed the PEP8 commits. Looks very good, thank you for fixing this! Merging