Diagnostics Crash on MacOS

[randomstring]

I have characterization data that I'm trying to analyze on my Mac. The Analyze Data works fine, however click any of the Diagnostic buttons crashes the app. Here is a sample stack trace

`2020-01-18 13:49:26.787 python3.7[52433:6406129] WARNING: <NSOpenPanel: 0x7fc19cb068c0> running implicitly; please run panels using NSSavePanel rather than NSApplication.
Fatal Python error: PyEval_RestoreThread: NULL tstate

Current thread 0x000000010aca5dc0 (most recent call first):
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/matplotlib/backends/backend_macosx.py", line 193 in mainloop
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 3309 in show
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/matplotlib/cbook/deprecation.py", line 413 in wrapper
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/matplotlib/pyplot.py", line 269 in show
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/frc_characterization/drive_characterization/data_analyzer.py", line 1173 in _plotVoltageDomain
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/frc_characterization/drive_characterization/data_analyzer.py", line 377 in plotVoltageDomain
File "/usr/local/Cellar/python/3.7.5/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/init.py", line 1705 in call
File "/usr/local/Cellar/python/3.7.5/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/init.py", line 1283 in mainloop
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/frc_characterization/drive_characterization/data_analyzer.py", line 1312 in main
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/frc_characterization/cli/init.py", line 41 in analyzerDrive
File "/Users/dole/.virtualenvs/py3/lib/python3.7/site-packages/frc_characterization/cli/init.py", line 90 in main
File "/Users/dole/.virtualenvs/py3/bin/frc-characterization", line 8 in
Abort trap: 6`

[randomstring]

I did several things to try and fix this. I reinstalled tcl-tk and python3 with no improvement. Ended up stumbling into this thread about mathplotlib failing on the mac pyenv/pyenv-virtualenv#140 and I created a ~/.mathplotrc file with the line backend : Agg in it and now frc-characterization is no longer crashing when generating the plots.

[pietroglyph]

Thank you for reminding me about this! I walked a user through diagnosing this issue on the FRC Discord and I made a branch with the fix, and then completely forgot to PR it!

[pietroglyph]

Please try pulling #89 and installing it locally (pip install git+https://github.com/pietroglyph/robot-characterization@mojave-fix --upgrade).