Remove dead FileNotFoundError

[asottile]

No description provided.

[codecov]

Codecov Report

Merging #618 into master will increase coverage by 1.56%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #618      +/-   ##
==========================================
+ Coverage   93.63%   95.19%   +1.56%     
==========================================
  Files          11       11              
  Lines        2358     2812     +454     
==========================================
+ Hits         2208     2677     +469     
+ Misses        150      135      -15

Impacted Files	Coverage Δ
tox/session.py	95.82% <ø> (+1.78%)	⬆️
tox/config.py	98.85% <0%> (+1.29%)	⬆️
tox/_pytestplugin.py	95.91% <0%> (+2.36%)	⬆️

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