Description

Currently the RTMClient makes use of collections.defaultDict in order to handle unregistered events. Since it's oftentimes not obvious what /all/ the methods are that you want to implement, it would be really nice if you could override that behavior by adding a handler for events that haven't been registered - then a user can log or do whatever else they want with those events.
Maybe it would be RTMClient.run_on(event='?')

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.