[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   |  Resolution:
Keywords:          |
-------------------+--------------------

Comment (by sa2ajj):

 After a bit of [source:master/buildbot/process/buildstep.py#L716 code
 reading] and thinking, it looks like this little snippet gives the same
 outcome:

 {{{
 a = u'Hello'
 b = a + ['world']
 }}}

--
Ticket URL: <http://trac.buildbot.net/ticket/2891#comment:1>
Buildbot <http://buildbot.net/>
Buildbot: build/test automation