error: add a new exception named WdirUnsupported This series intents to support wdir() predicate with different operators like ~, ^. Currently the storage class don't support wdir(). This exception is introduced so that it can be raised from places where wdir() is passed and is not supported and we can catch this where we want to support the predicate. Also throwing an error at low level and catching at some higher level is better than using if-else especially for perf.