Martin: Sorry for missing that line.

Under https, byte iterable seems has not been supported:
>>> r = Request('https://www.python.org', {b'post': 'data'}, {'Content-Length':10})
>>> urlopen(r)

... hanging here...

Meanwhile, I assumed bytearray works as expected.
>>> r = Request('https://www.python.org', bytearray('post=data', 'utf-8'))
>>> urlopen(r)
....
....
urllib.error.HTTPError: HTTP Error 403: FORBIDDEN

In *4.patch, I updated Request class doc to add these observations and fixed issues appeared in last patch.