I've updated my PR to reflect a better message for the IncompleteReadError exception. When expected is None, the error reads, "IncompleteReadError: 1 bytes read on a total of None expected bytes" which is confusing. My PR changes this to "IncompleteReadError: 1 bytes read on a total of unknown expected bytes". Otherwise, it is required that whoever views the exception text(possibly through layers of abstraction), to know that None(a "low level" programmers decision) is equal to unknown.