Use .is_file() instead of .exists() not to find directory with the sa…

[atztogo]

…me name

[codecov-commenter]

Codecov Report

❌ Patch coverage is 84.21053% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.90%. Comparing base (4f2ebe0) to head (fc4b17d).
⚠️ Report is 84 commits behind head on develop.

Files with missing lines	Patch %	Lines
test/cui/test_phelel_cui.py	80.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #126      +/-   ##
===========================================
+ Coverage    72.07%   72.90%   +0.82%     
===========================================
  Files           81       81              
  Lines         5791     5982     +191     
===========================================
+ Hits          4174     4361     +187     
- Misses        1617     1621       +4     

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