fix: workaround for coverage bug

[alexander-held]

The fit function in the CLI has the structure

https://github.com/alexander-held/cabinetry/blob/d888ec054e080f474a12de6de375857631c55987/src/cabinetry/cli/__init__.py#L134-L137

and both branches are tested:

https://github.com/alexander-held/cabinetry/blob/d888ec054e080f474a12de6de375857631c55987/tests/cli/test_cli.py#L172-L182

In CI, where the coverage is calculated with Python 3.7, everything shows up as covered. When using Python 3.8 it does not. This is presumably due to a CPython optimization, and can seemingly be fixed by the addition of a pass:

https://github.com/alexander-held/cabinetry/blob/1a11641e214072c3922d7a1269304c97754496b8/src/cabinetry/cli/__init__.py#L138

This PR adds this pass and a link to a coverage issue which discusses what I believe is the same underlying issue.

[codecov]

Codecov Report

Merging #234 (dd3a270) into master (612b3cf) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #234   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines         1727      1728    +1     
  Branches       268       268           
=========================================
+ Hits          1727      1728    +1     

Impacted Files	Coverage Δ
src/cabinetry/cli/__init__.py	100.00% <100.00%> (ø)

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[alexander-held]

The CI seems unstable, it sometimes passes and sometimes fails. This was also observed in https://github.com/alexander-held/cabinetry/actions/runs/962573993. Possibly related to the release of numpy 1.21. #235 seems to fix this.