Simplify strError tests to avoid differencies between platforms

[piponazo]

This PR fixes #763. This PR fixes #803.

I simplified the tests for strError so that we do not need to write complex if-else preprocessor conditions to check the slightly different messages in every platform.

[D4N]

Lgtm, but gitlab is unhappy

[piponazo]

Damn it ... gmock is not available in some of the Gitlab distros. I'll work to bring it. I expect to use GMock to mock some classes in the future.

[clanmills]

You may (or may not) find my notes helpful: #575

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@c6d1470). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #802   +/-   ##
=========================================
  Coverage          ?   70.79%           
=========================================
  Files             ?      145           
  Lines             ?    19081           
  Branches          ?        0           
=========================================
  Hits              ?    13509           
  Misses            ?     5572           
  Partials          ?        0

Impacted Files	Coverage Δ
unitTests/test_futils.cpp	100% <100%> (ø)

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[D4N]

I've tried adding gmock in via 38b8ad7, let's see whether that works.

[nehaljwani]

CI is happy now!

[piponazo]

Now, I only need an approval! 😇

[D4N]

I'll cleanup the commit log, then I'll approve.