[Buildbot] #3435: Install docs dependencies in setup.py

[Buildbot trac]

#3435: Install docs dependencies in setup.py
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Reporter:  dustin     |       Owner:  dustin
    Type:  undecided  |      Status:  new
Priority:  minor      |   Milestone:  0.9.+
 Version:             |  Resolution:
Keywords:             |
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Comment (by rutsky):

 When `buildbot[docs]` will be merged, please update
 [https://github.com/buildbot/buildbot/blob/master/rtd-requirements.txt
 rtd-requirements.txt] file.

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Ticket URL: <http://trac.buildbot.net/ticket/3435#comment:7>
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