[Buildbot] #3566: fix compatibility fix flake8 2.6.0

[Buildbot trac]

#3566: fix compatibility fix flake8 2.6.0
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Reporter:  tardyp     |      Owner:
    Type:  undecided  |     Status:  new
Priority:  major      |  Milestone:  0.9.+
 Version:  master     |   Keywords:
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 flake8 2.6.0 broke travis, and we need to remove the fix to 2.5.5

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Ticket URL: <http://trac.buildbot.net/ticket/3566>
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Buildbot: build/test automation