jwt.exceptions.InvalidSignatureError: Signature verification failed

[nilp0inter]

The master output this warning when a browser connects to it:

deeptracy-buildbot_1  |         Traceback (most recent call last):
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/twisted/web/server.py", line 481, in getSession
deeptracy-buildbot_1  |             session = self.site.getSession(sessionCookie)
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/buildbot/www/service.py", line 174, in getSession
deeptracy-buildbot_1  |             return BuildbotSession(self, uid)
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/buildbot/www/service.py", line 74, in __init__
deeptracy-buildbot_1  |             self._fromToken(token)
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/buildbot/www/service.py", line 88, in _fromToken
deeptracy-buildbot_1  |             log.err(e, "while decoding JWT session")
deeptracy-buildbot_1  |         --- <exception caught here> ---
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/buildbot/www/service.py", line 84, in _fromToken
deeptracy-buildbot_1  |             SESSION_SECRET_ALGORITHM])
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/jwt/api_jwt.py", line 93, in decode
deeptracy-buildbot_1  |             jwt, key=key, algorithms=algorithms, options=options, **kwargs
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/jwt/api_jws.py", line 157, in decode
deeptracy-buildbot_1  |             key, algorithms)
deeptracy-buildbot_1  |           File "/usr/local/lib/python3.6/site-packages/jwt/api_jws.py", line 224, in _verify_signature
deeptracy-buildbot_1  |             raise InvalidSignatureError('Signature verification failed')
deeptracy-buildbot_1  |         jwt.exceptions.InvalidSignatureError: Signature verification failed
deeptracy-buildbot_1  | 

Related to #96 .

[kjcole]

I'm new to both testing and CI. I'm going through the BuildBot tutorial, and found the above error in twistd.log.