[Python-3000] fix email module for bytes/str

[Victor Stinner]

Hi,

I started to work on email module, but I have trouble to understand if a 
function should returns bytes or str (because I don't know email module).

Header.encode() -> bytes?
Message.as_string() -> bytes?
decode_header() -> list of (bytes, str|None) or (str, str|None)?
base64MIME.encode() -> bytes?

message_from_string() <- bytes?

Message.get_payload() -> bytes or str?

A charset name type is str, right?

---------------

Things to change to get bytes:
 - replace StringIO with BytesIO
 - add 'b' prefix, eg. '' becomes b''
 - replace "%s=%s" % (x, y) with b''.join((x, b'=', y))
   => is it the best method to concatenate bytes?

Problems (to port python 2.x code to 3000):
 - When obj.lower() is used, I expect obj to be str but it's bytes
 - obj.strip() doesn't work when obj is a byte, it requires an
   argument but I don't know the right value! Maybe b'\n\r\v\t '?
 - iterate on a bytes object gives number and not bytes object, eg.
      for c in b"small text":
         if re.match("(\n|\r)", c): ...
   Is it possible to 'bytes' regex? re.compile(b"x") raise an exception

-- 
Victor Stinner aka haypo
http://hachoir.org/