FIX: detect ill-pose sampling-strategy as a float

[glemaitre]

Fixes corner case with understandable errors. Crashing was happening when:

• a ratio was given forcing to generate new-sample in under-sampling methods,
• a ratio was given forcing to remove sample in over-sampling methods.

[pep8speaks]

Hello @glemaitre! Thanks for updating the PR.

• There are no PEP8 issues in the file imblearn/utils/_validation.py !

• There are no PEP8 issues in the file imblearn/utils/tests/test_validation.py !

Comment last updated on November 17, 2018 at 10:37 Hours UTC

[codecov]

Codecov Report

Merging #507 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #507      +/-   ##
==========================================
+ Coverage   98.86%   98.86%   +<.01%     
==========================================
  Files          82       82              
  Lines        5020     5023       +3     
==========================================
+ Hits         4963     4966       +3     
  Misses         57       57

Impacted Files	Coverage Δ
imblearn/utils/tests/test_validation.py	100% <100%> (ø)	⬆️
imblearn/utils/_validation.py	100% <100%> (ø)	⬆️

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