Problem with imap4-utf-7 on Debian 11 and Python 3.9

[psztoch]

LookupError unknown encoding: imap4-utf-7

490:                flags = flags.split(" ")
491:                name = bytearray(name, "utf-8")
>>492:              name = name.decode("imap4-utf-7")
493:                mdm_found = False

/srv/modoboa/env/lib/python3.9/site-packages/modoboa_webmail/lib/imaputils.py in _listmboxes, line 492 ['.', '', '/usr/lib/python39.zip', '/usr/lib/python3.9', '/usr/lib/python3.9/lib-dynload', '/srv/modoboa/env/lib/python3.9/site-packages']

Modules version:

modoboa-1.17.0.dist-info                                                                                                                                                                                                                                                                modoboa_amavis-1.3.1.dist-info                                                                                                                                                                                                                                                          modoboa_contacts-0.8.2.dist-info
modoboa_pdfcredentials-1.4.0.dist-info
modoboa_postfix_autoreply-1.6.1.dist-info
modoboa_radicale-1.5.1.dist-info
modoboa_sievefilters-1.5.0.dist-info
modoboa_webmail-1.6.1.dist-info

[psztoch]

Patch for /srv/modoboa/env/lib/python3.9/site-packages/modoboa/lib/imap_utf7.py

 def imap4_utf_7(name):
-    if name == "imap4-utf-7":
+    if name == "imap4-utf-7" or name == "imap4_utf_7":
         return (encoder, decoder, StreamReader, StreamWriter)

[tonioo]

@psztoch Thanks for the fix but could you create a PR?