Fixes no funcargs

[chinghwayu]

Fixes #122

Based on:
ionelmc/pytest-benchmark@d1ab766

[codecov-commenter]

Codecov Report

Merging #123 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #123   +/-   ##
=======================================
  Coverage   90.85%   90.85%           
=======================================
  Files         107      107           
  Lines        4318     4319    +1     
=======================================
+ Hits         3923     3924    +1     
  Misses        395      395           

Impacted Files	Coverage Δ
pytest_cases/plugin.py	90.30% <100.00%> (+0.02%)	⬆️

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[smarie]

Thanks @chinghwayu , this looks good to me.

(and travis seems happy https://travis-ci.org/github/smarie/python-pytest-cases/builds/715678818 )