removeRegisteredPrefix does not seem to work as expected
For other libraries,
prefixId = face.registerPrefix(prefix, onInterest, onRegisterFailed)
Should be able to remove the registered prefix from local registeredPrefixTable, but for PyNDN2, returned prefixId is none-type.
Adding "return" at face.py, line 286(https://github.com/named-data/PyNDN2/blob/master/python/pyndn/face.py#L286) fixes it...