Failes to enable plugin with trac 0.11.3

[superna@…]

Traceback (most recent call last):

File "/local/engine/trac/trac/web/api.py", line 367, in send_error

'text/html')

File "/local/engine/trac/trac/web/chrome.py", line 688, in render_template

data = self.populate_data(req, data)

File "/local/engine/trac/trac/web/chrome.py", line 596, in populate_data

dchrome?.update(req.chrome)

File "/local/engine/trac/trac/web/api.py", line 194, in getattr

value = self.callbacks[name](self)

File "/local/engine/trac/trac/web/chrome.py", line 464, in prepare_request

for category, name, text in contributor.get_navigation_items(req):

File "build/bdist.linux-i686/egg/TracBuildbot/web_ui.py", line 33, in get_navigation_items

yield 'mainnav', 'buildbot', Markup('$$REMOVED$$Buildbot$$', self.env.href.buildbot())

LookupError: unknown encoding: /trac/linux/buildbot