Adding another check to _check_corpus_sanity for compressed files, adding test

[dchaplinsky]

Closes #3246

[codecov]

Codecov Report

Merging #3258 (3be4190) into develop (e51288c) will increase coverage by 0.44%.
The diff coverage is 80.00%.

@@             Coverage Diff             @@
##           develop    #3258      +/-   ##
===========================================
+ Coverage    78.88%   79.32%   +0.44%     
===========================================
  Files           68       68              
  Lines        11772    11777       +5     
===========================================
+ Hits          9286     9342      +56     
+ Misses        2486     2435      -51     

Impacted Files	Coverage Δ
gensim/models/word2vec.py	89.70% <80.00%> (-0.07%)	⬇️
gensim/utils.py	71.54% <0.00%> (+0.48%)	⬆️
gensim/corpora/wikicorpus.py	93.75% <0.00%> (+11.53%)	⬆️
gensim/scripts/segment_wiki.py	92.37% <0.00%> (+21.18%)	⬆️

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[dchaplinsky]

Hello @piskvorky
Anything else needs to be done on this one?

[piskvorky]

Looks good to me, thanks! Now let's wait for @mpenkov 's review and merge, thanks for your patience.