Support Python 3 Base WMI

[nmuesch]

What does this PR do?

Supports Python3 for the base classes of the WMI check

The biggest change here is the way the metaclass is defined. In Python3, you can no longer do the metaclass approach and need to put it in the declaration of the class itself. Six provides a way to be compatible with both, so I used that.

PEP that changes this - https://www.python.org/dev/peps/pep-3115/

Also, map was returning the map type, so you couldn't add a map to a list, this casts the map to the underlying type of list.

Motivation

🐍3️⃣

Review checklist

• PR has a meaningful title or PR has the no-changelog label attached
• Feature or bugfix has tests
• Git history is clean
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo
• If PR adds a configuration option, it has been added to the configuration file.

Additional Notes

Anything else we should know when reviewing?

[codecov-io]

Codecov Report

Merging #3036 into master will decrease coverage by 8.77%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3036      +/-   ##
==========================================
- Coverage   84.23%   75.45%   -8.78%     
==========================================
  Files         666       46     -620     
  Lines       35945     3573   -32372     
  Branches     4266      427    -3839     
==========================================
- Hits        30278     2696   -27582     
+ Misses       4422      768    -3654     
+ Partials     1245      109    -1136

[gmmeyer]

looks good to me