Connection errors with cqlsh and other DSE tools 

Troubleshooting for permissions when credentials are required.

If authentication_options are enabled (true) in the dse.yaml, credentials are required to launch cqlsh and other tools:
cqlsh -u username -p password
If a client connection is attempted without permissions, the following error occurs:
Connection error: ('Unable to connect to any servers', {'127.0.0.1': error(111, "Tried connecting to [('127.0.0.1', 9042)]. Last error: Connection refused")})
See Providing credentials with cqlsh and Providing credentials with DSE tools.