[Buildbot] #2891: Exception when using Interpolate in description

[Buildbot trac]

#2891: Exception when using Interpolate in description
-------------------+-------------------
Reporter:  sa2ajj  |      Owner:
    Type:  defect  |     Status:  new
Priority:  major   |  Milestone:  0.9.+
 Version:  0.8.9   |   Keywords:
-------------------+-------------------
 Per discussion at
 [http://irclogs.jackgrigg.com/irc.freenode.net/buildbot/2014-09-09#i_3443770
 IRC]:

 This step:

 {{{
         build_factory.addStep(ShellCommand(
                 command=['cmd', 'param', ..., 'param'],
         haltOnFailure=True,
         #description=Interpolate("configure %(prop:Environment)s"),
         description="configure the new environment",
         doStepIf=lambda step: step.build.getProperty("state") == "present"
         ))
 }}}

 causes an exception

 {{{
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py",
 line 1155, in gotResult
     _inlineCallbacks(r, g, deferred)
   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py",
 line 1142, in _inlineCallbacks
     deferred.callback(e.value)
   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py",
 line 382, in callback
     self._startRunCallbacks(result)
   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py",
 line 490, in _startRunCallbacks
     self._runCallbacks()
 --- <exception caught here> ---
   File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py",
 line 577, in _runCallbacks
     current.result = callback(current.result, *args, **kw)
   File "/usr/local/lib/python2.7/dist-
 packages/buildbot/process/buildstep.py", line 653, in _gotResults
     self.setStatus(cmd, results)
   File "/usr/local/lib/python2.7/dist-
 packages/buildbot/process/buildstep.py", line 739, in setStatus
     self._step_status.setText(self.getText(cmd, results))
   File "/usr/local/lib/python2.7/dist-
 packages/buildbot/process/buildstep.py", line 716, in getText
     return self.describe(True) + ["failed"]
 exceptions.TypeError: coercing to Unicode: need string or buffer, list
 found
 }}}

--
Ticket URL: <http://trac.buildbot.net/ticket/2891>
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Buildbot: build/test automation