'ascii' codec can't encode character u'\u0308'

Noticed this error in a svn up step:

Traceback (most recent call last):
File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 651, in _runCallbacks
current.result = callback(current.result, *args, **kw)
File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1355, in gotResult
_inlineCallbacks(r, g, deferred)
File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1297, in _inlineCallbacks
result = result.throwExceptionIntoGenerator(g)
File "/usr/lib64/python2.7/site-packages/twisted/python/failure.py", line 389, in throwExceptionIntoGenerator
return g.throw(self.type, self.value, self.tb)
--- ---
File "/usr/lib/python2.7/site-packages/buildbot/process/buildstep.py", line 577, in startStep
self.results = yield self.run()
File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 1299, in _inlineCallbacks
result = g.send(result)
File "/usr/lib/python2.7/site-packages/buildbot/process/buildstep.py", line 707, in run
results = yield self._start_deferred
File "/usr/lib64/python2.7/site-packages/twisted/internet/defer.py", line 651, in _runCallbacks
current.result = callback(current.result, *args, **kw)
File "/usr/lib/python2.7/site-packages/buildbot/steps/source/svn.py", line 356, in parseAndRemove
for filename in self.getUnversionedFiles(stdout, self.keep_on_purge):
File "/usr/lib/python2.7/site-packages/buildbot/steps/source/svn.py", line 379, in getUnversionedFiles
result_xml = xml.dom.minidom.parseString(xmlStr)
File "/usr/lib64/python2.7/xml/dom/minidom.py", line 1931, in parseString
return expatbuilder.parseString(string)
File "/usr/lib64/python2.7/xml/dom/expatbuilder.py", line 940, in parseString
return builder.parseString(string)
File "/usr/lib64/python2.7/xml/dom/expatbuilder.py", line 223, in parseString
parser.Parse(string, True)
exceptions.UnicodeEncodeError: 'ascii' codec can't encode character u'\u0308' in position 244: ordinal not in range(128)