carbon-cache start failure: TypeError: unhashable type: 'MethodicalState'

I just tried to install and carbon-cache fails to start with this error:

service carbon-cache start Starting carbon-cache-1: Traceback (most recent call last): File "/opt/graphite/bin/carbon-cache.py", line 32, in run_twistd_plugin(file) File "/opt/graphite/lib/carbon/util.py", line 96, in run_twistd_plugin runApp(config) File "/usr/local/lib/python2.7/dist-packages/twisted/scripts/twistd.py", line 25, in runApp _SomeApplicationRunner(config).run() File "/usr/local/lib/python2.7/dist-packages/twisted/application/app.py", line 380, in run self.application = self.createOrGetApplication() File "/usr/local/lib/python2.7/dist-packages/twisted/application/app.py", line 440, in createOrGet Application ser = plg.makeService(self.config.subOptions) File "/opt/graphite/lib/twisted/plugins/carbon_cache_plugin.py", line 20, in makeService from carbon import service File "/opt/graphite/lib/carbon/service.py", line 18, in from twisted.application.internet import TCPServer, TCPClient File "/usr/local/lib/python2.7/dist-packages/twisted/application/internet.py", line 542, in class _ClientMachine(object): File "/usr/local/lib/python2.7/dist-packages/twisted/application/internet.py", line 842, in _Clien tMachine outputs=[_connect]) File "/usr/local/lib/python2.7/dist-packages/automat/_methodical.py", line 62, in upon self.machine._oneTransition(self, input, enter, outputs, collector) File "/usr/local/lib/python2.7/dist-packages/automat/_methodical.py", line 255, in _oneTransition tuple(outputTokens)) File "/usr/local/lib/python2.7/dist-packages/automat/_core.py", line 74, in addTransition (inState, inputSymbol, outState, tuple(outputSymbols)) TypeError: unhashable type: 'MethodicalState' failed carbon-cache-1 not running

obfuscurity / synthesize

carbon-cache start failure: TypeError: unhashable type: 'MethodicalState' #64