As https://wiki.onap.org/download/attachments/93000392/CPS-231.mp4?version=2&modificationDate=1614013592000&api=v2 showed current in incorrect (invalid) CpsPath returns a 501 'Internal server' error which can be misleading for an end-user. This user story is to propose and implement better error handling.

Acceptance Criteria

• Discuss and agree with team on correct error message/error code for invalid cps path 
• update https://wiki.onap.org/display/DW/CPS+Exceptions+and+REST+API+HTTP+Response+Codes
• Implement error handling as agreed in NF-Proxy and CPS-Core