`imaplib.IMAP4.error: None`

[vpanteleev-sym]

Bug report

Checklist

• I am confident this is a bug in CPython, not a bug in a third-party project
• I have searched the CPython issue tracker,
  and am confident this bug has not been reported before

CPython versions tested on:

3.11

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.11.3 (main, Jun 5 2023, 09:32:32) [GCC 13.1.1 20230429]

A clear and concise description of the bug:

import imaplib

imaplib.IMAP4_SSL('outlook.office365.com', port=995)

Output:

Traceback (most recent call last):
  File "/home/vladimir/tmp/2023-08-22-scratch/11:33:20/./test.py", line 3, in <module>
    imaplib.IMAP4_SSL('outlook.office365.com', port=995)
  File "/usr/lib/python3.11/imaplib.py", line 1323, in __init__
    IMAP4.__init__(self, host, port, timeout)
  File "/usr/lib/python3.11/imaplib.py", line 205, in __init__
    self._connect()
  File "/usr/lib/python3.11/imaplib.py", line 253, in _connect
    raise self.error(self.welcome)
imaplib.IMAP4.error: None

Regardless of anything, I don't think None should show up as the error message.

Linked PRs

• gh-108280: Give a meaningful error for an invalid imaplib greeting #152768
• [3.15] gh-108280: Give a meaningful error for an invalid imaplib greeting (GH-152768) #152856
• [3.14] gh-108280: Give a meaningful error for an invalid imaplib greeting (GH-152768) #152857
• [3.13] gh-108280: Give a meaningful error for an invalid imaplib greeting (GH-152768) #152858

[ericvsmith]

I agree on not showing None.

If you set imaplib.Debug to 5 before the IMAP4_SSL call, you get something like:

  18:16.98 imaplib version 2.58
  18:16.98 new IMAP4 connection, tag=b'LEDL'
  18:17.03 < b'+OK The Microsoft Exchange POP3 service is ready. [QgBMAEEAUABSADAAMwBDAEEAMAAwADUANwAuAG4AYQBtAHAAcgBkADAAMwAuAHAAcg
BvAGQALgBvAHUAdABsAG8AbwBrAC4AYwBvAG0A]'
  18:17.03      matched b'\\+( (?P<data>.*))?' => (None, None)

I haven't dug into it enough to know why it doesn't like the message returned by outlook.office365.com.

[vpanteleev-sym]

I haven't dug into it enough to know why it doesn't like the message returned by outlook.office365.com.

As I found out, I was accidentally using the POP3 port instead of the IMAP port, which probably explains why it raises an exception (though not the error message, of course).

[serhiy-storchaka]

Fixed in #152768. imaplib now reports a meaningful error for an invalid greeting instead of error: None.