fix magic errors not causing failure

[alex-treebeard]

#77

[codecov]

Codecov Report

Merging #78 (778d9c5) into main (966edac) will decrease coverage by 1.05%.
The diff coverage is 84.21%.

❗ Current head 778d9c5 differs from pull request most recent head e048648. Consider uploading reports for the commit e048648 to get more accurate results

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
- Coverage   92.46%   91.41%   -1.06%     
==========================================
  Files           4        4              
  Lines         146      163      +17     
==========================================
+ Hits          135      149      +14     
- Misses         11       14       +3     

Impacted Files	Coverage Δ
src/nbmake/pytest_plugin.py	91.30% <80.00%> (-3.44%)	⬇️
src/nbmake/nb_run.py	92.30% <85.71%> (-1.54%)	⬇️