fixed pep8 compliance in test file

[kognate]

Fixes #157

[codecov-io]

Codecov Report

Merging #158 into master will decrease coverage by -2.53%.

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
- Coverage    82.1%   79.57%   -2.53%     
==========================================
  Files          24       24              
  Lines        1028     1028              
==========================================
- Hits          844      818      -26     
- Misses        184      210      +26

Impacted Files	Coverage Δ
watson_developer_cloud/language_translator_v2.py	44.82% <ø> (-31.04%)	❌
..._developer_cloud/watson_developer_cloud_service.py	65.07% <ø> (-6.88%)	❌
watson_developer_cloud/dialog_v1.py	38.88% <ø> (-5.56%)	❌
watson_developer_cloud/document_conversion_v1.py	93.75% <ø> (-3.13%)	❌

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