Don't expect trailing space on command completion

While trying to see why I couldn't get my emails from an Exchange server
I found this:

[imap]: 41:31.42 someserver.com handler _put_response(IOMC1 OK)
[imap]: 41:31.42 someserver.com handler unexpected response: 'IOMC1 OK'

And shortly after that the connection was closed. IOMC1 is just the
unique tag for the session.

The pattern looks for the tag, a number, a word like "OK" or something,
*then a space*, then optionally some data.

If the data aren't there it shouldn't be expecting a space.

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/bundled_imaplib2.py

@@ -342,7 +342,7 @@ class IMAP4(object):
         self.tagpre = Int2AP(random.randint(4096, 65535))
         self.tagre = re.compile(r'(?P<tag>'
                         + self.tagpre
-                        + r'\d+) (?P<type>[A-Z]+) (?P<data>.*)')
+                        + r'\d+) (?P<type>[A-Z]+) ?(?P<data>.*)')
 
         self._mode_ascii()	# Only option in py2