[Buildbot] #3085: use some Jinja2 fanciness to make sure secrets exist

[Buildbot trac]

#3085: use some Jinja2 fanciness to make sure secrets exist
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Reporter:  dustin            |       Owner:
    Type:  enhancement       |      Status:  new
Priority:  patches-accepted  |   Milestone:  sys - other
 Version:  0.8.9             |  Resolution:
Keywords:  ansible           |
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Comment (by sa2ajj):

 To avoid empty strings I added the following to our `ansible.cfg`:

 {{{
 error_on_undefined_vars = True
 }}}

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Ticket URL: <http://trac.buildbot.net/ticket/3085#comment:1>
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