fix #4243 - support positional argument stacklevel on python2

[RonnyPfannschmidt]

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[codecov]

Codecov Report

Merging #4244 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4244      +/-   ##
==========================================
- Coverage   95.87%   95.86%   -0.01%     
==========================================
  Files         109      109              
  Lines       24590    24597       +7     
  Branches     2392     2394       +2     
==========================================
+ Hits        23575    23580       +5     
- Misses        720      721       +1     
- Partials      295      296       +1

Flag	Coverage Δ
#docs	29.04% <38.46%> (-0.02%)	⬇️
#doctesting	29.04% <38.46%> (-0.02%)	⬇️
#linting	29.04% <38.46%> (-0.02%)	⬇️
#linux	95.64% <100%> (-0.01%)	⬇️
#nobyte	92.02% <100%> (+0.64%)	⬆️
#numpy	93.02% <100%> (+51.33%)	⬆️
#pexpect	41.67% <0%> (-0.02%)	⬇️
#py27	94.05% <100%> (ø)	⬆️
#py34	92.34% <30.76%> (+0.14%)	⬆️
#py35	92.35% <30.76%> (+0.02%)	⬆️
#py36	93.98% <30.76%> (-0.02%)	⬇️
#py37	92.36% <30.76%> (+0.02%)	⬆️
#trial	93.02% <100%> (+51.33%)	⬆️
#windows	94.13% <100%> (+0.75%)	⬆️
#xdist	93.89% <100%> (+0.15%)	⬆️

Impacted Files	Coverage Δ
testing/test_recwarn.py	99.56% <100%> (ø)	⬆️
src/_pytest/recwarn.py	98.31% <100%> (+0.04%)	⬆️
src/_pytest/capture.py	93.39% <0%> (-0.46%)	⬇️

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[nicoddemus]

Thanks