CI/Tests failing

[gordonwatts]

They just started failing quietly a few months ago. This PR will get everything working again.

• Fixed issues where black had reformatted code so that we couldn't tell where one method started and the other ended.
• Modern version of flake8 is catching more errors now.
• The python 3.7 on macOS failure may have been suprious - it seems to work currently on the CI infrastructure.

Fixes #214

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a284336) 95.15% compared to head (242e8f0) 95.05%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #215      +/-   ##
==========================================
- Coverage   95.15%   95.05%   -0.11%     
==========================================
  Files          35       35              
  Lines        1880     1880              
  Branches      249      249              
==========================================
- Hits         1789     1787       -2     
- Misses         59       60       +1     
- Partials       32       33       +1     

Flag	Coverage Δ
unittests	95.05% <100.00%> (-0.11%)	⬇️

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Files	Coverage Δ
func_adl_xAOD/common/ast_to_cpp_translator.py	88.04% <100.00%> (-0.42%)	⬇️

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