Performative check

[Karrenbelt]

Ledger and contract api calls can result in an incorrect (e.g. error) performative. We should return specific failure response, and deal with this event separately. We might also raise a custom IncorrectPerformativeError which can be intercepted at the level of the round, where all errors may transition to PathSelectionRound.

[Karrenbelt]

addressed in #106 and #107. In case of an incorrect performative (e.g. error response from contract call) the behaviours return None and the agents do not deliver a payload. This is probably not ideal because once reset hits it will transition to the same round. Instead an ErrorPayload may be considered, an on a majority vote a transition back to the initial PathSelection. Eventually, repeated and continuous cycling back to PathSelectionRound with ErrorPayload the application may transition into a degenerate round (Event.UNKNOWN_HEALTH_ISSUE)

[Karrenbelt]

TODO:

Address inconsistencies in error handling: #106 (comment)