Testing on python 3.8

[jenshnielsen]

Since its scheduled for release soon
There are a few outstanding questions.

• Most packages are not available as wheels yet so add a bunch of dependencies to build from source. This does initially take more time but caching should take care of this in the following builds.
• Pyqt5 is not available from pypi as whl or as source so skip it completely for 3.8
• Some docs examples require pyqt5 so skip building the docs for 3.8 for now
• There are a bunch of new deprecation warnings. I am planing on fixing these in a new pr

[codecov]

Codecov Report

Merging #1722 into master will increase coverage by 0.1%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #1722     +/-   ##
=========================================
+ Coverage   67.21%   67.32%   +0.1%     
=========================================
  Files         146      146             
  Lines       18001    18073     +72     
=========================================
+ Hits        12100    12167     +67     
- Misses       5901     5906      +5