[Q] unable to start carbon - TypeError: unhashable type: 'MethodicalState'

[aamerik]

Having trouble starting 1.1.6 and 1.1.7 using python 3.6.8 venv on cent7 due to the exception below:

/opt/graphite/bin/carbon-cache.py start
Starting carbon-cache (instance a)
Traceback (most recent call last):
File "/opt/graphite/bin/carbon-cache.py", line 32, in
run_twistd_plugin(file)
File "/opt/graphite/lib64/python3.6/site-packages/carbon/util.py", line 140, in run_twistd_plugin
runApp(config)
File "/opt/graphite/lib64/python3.6/site-packages/twisted/scripts/twistd.py", line 25, in runApp
runner.run()
File "/opt/graphite/lib64/python3.6/site-packages/twisted/application/app.py", line 381, in run
self.application = self.createOrGetApplication()
File "/opt/graphite/lib64/python3.6/site-packages/twisted/application/app.py", line 448, in createOrGetApplication
ser = plg.makeService(self.config.subOptions)
File "/opt/graphite/lib64/python3.6/site-packages/twisted/plugins/carbon_cache_plugin.py", line 20, in makeService
from carbon import service
File "/opt/graphite/lib64/python3.6/site-packages/carbon/service.py", line 18, in
from twisted.application.internet import TCPServer
File "/opt/graphite/lib64/python3.6/site-packages/twisted/application/internet.py", line 548, in
class _ClientMachine(object):
File "/opt/graphite/lib64/python3.6/site-packages/twisted/application/internet.py", line 947, in _ClientMachine
outputs=[_connect])
File "/opt/graphite/lib64/python3.6/site-packages/automat/_methodical.py", line 56, in upon
self.machine._oneTransition(self, input, enter, outputs, collector)
File "/opt/graphite/lib64/python3.6/site-packages/automat/_methodical.py", line 249, in _oneTransition
tuple(outputTokens))
File "/opt/graphite/lib64/python3.6/site-packages/automat/_core.py", line 74, in addTransition
(inState, inputSymbol, outState, tuple(outputSymbols))
TypeError: unhashable type: 'MethodicalState'

I did not have any issues installing the following pip modules in this virtualenv:

pip list
Package Version

---

attrs 20.3.0
Automat 0.4.0
cachetools 4.2.1
carbon 1.1.6
constantly 15.1.0
hyperlink 21.0.0
idna 3.1
incremental 21.3.0
pip 21.0.1
PyHamcrest 2.0.2
setuptools 54.1.2
six 1.15.0
Twisted 20.3.0
txAMQP 0.8.2
urllib3 1.26.4
virtualenv 15.1.0
whisper 1.1.6
zope.interface 5.2.0

any help is appreciated thank you

[aamerik]

appears to be related to automat version.