imap4-utf-7 encoding not known

[cl-parsons]

OS : Debian Bullseye (11.2)
Python : 3.9.2
Virtualenv : Yes

### How to reproduce :

Modoboa installed and working flawlessly

Modoboa-sievefilters activated

Create a filter and try to add a rule -> Internal Server Error

Log :

Internal Server Error: /sfilters/main/newfilter/

LookupError at /sfilters/main/newfilter/
unknown encoding: imap4-utf-7

Request Method: GET
Request URL: https://listonmail.fr/sfilters/main/newfilter/
Django Version: 2.2.27
Python Executable: /usr/bin/python3
Python Version: 3.9.2
Python Path: ['/opt/modoboa/listonmail_fr', '/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages', '/usr/lib/python39.zip', '/usr/lib/python3.9', '/usr/lib/python3.9/lib-dynload', '/usr/local/lib/python3.9/dist-packages', '/usr/lib/python3/dist-packages']
Server time: Thu, 24 Feb 2022 13:32:35 +0100
Installed Applications:
('django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.sites',
 'django.contrib.staticfiles',
 'reversion',
 'ckeditor',
 'ckeditor_uploader',
 'rest_framework',
 'rest_framework.authtoken',
 'drf_spectacular',
 'phonenumber_field',
 'django_otp',
 'django_otp.plugins.otp_totp',
 'django_otp.plugins.otp_static',
 'modoboa',
 'modoboa.core',
 'modoboa.lib',
 'modoboa.admin',
 'modoboa.transport',
 'modoboa.relaydomains',
 'modoboa.limits',
 'modoboa.parameters',
 'modoboa.dnstools',
 'modoboa.policyd',
 'modoboa.maillog',
 'modoboa_sievefilters')
Installed Middleware:
('x_forwarded_for.middleware.XForwardedForMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django_otp.middleware.OTPMiddleware',
 'modoboa.core.middleware.TwoFAMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.locale.LocaleMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'modoboa.core.middleware.LocalConfigMiddleware',
 'modoboa.lib.middleware.AjaxLoginRedirect',
 'modoboa.lib.middleware.CommonExceptionCatcher',
 'modoboa.lib.middleware.RequestCatcherMiddleware')


Traceback:

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/django/core/handlers/exception.py" in inner
  34.             response = get_response(request)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/django/core/handlers/base.py" in _get_response
  115.                 response = self.process_exception_by_middleware(e, request)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/django/core/handlers/base.py" in _get_response
  113.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/lib/python3.9/contextlib.py" in inner
  79.                 return func(*args, **kwds)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/django/contrib/auth/decorators.py" in _wrapped_view
  21.                 return view_func(request, *args, **kwargs)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa/admin/lib.py" in wrapped_f
  40.                 return f(request, *args, **kwargs)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/views.py" in newfilter
  164.     form = FilterForm(conds, actions, request)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/forms.py" in __init__
  56.             getattr(self, "_build_%s_field" % a[0])(request, *a[1:])

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/forms.py" in _build_fileinto_field
  137.         self._build_action_field(request, "fileinto", *values)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/forms.py" in _build_action_field
  124.                 choices = getattr(self, arg["vloader"])(request)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/forms.py" in userfolders
  160.         ret = mbc.getmboxes(request.user)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/imaputils.py" in getmboxes
  228.         self._listmboxes(topmailbox, md_mailboxes)

File "/opt/modoboa/venv_2.0.0-beta.3/lib/python3.9/site-packages/modoboa_sievefilters/imaputils.py" in _listmboxes
  184.             name = name.decode("imap4-utf-7")

Exception Type: LookupError at /sfilters/main/newfilter/
Exception Value: unknown encoding: imap4-utf-7

Proposal to resolve

apt-get install python3-imaplib2

Things to improve

Add the instruction to the documentation.

[cl-parsons]

Ok, I continued my test and the installation of imaplib2 does not resolve the problem.

If I do the following :

abc = bytearray('foobar', 'utf-8')
abc.decode('imap4-utf-7')

I get the error.

If I do

abc = bytearray()
abc.decode('imap4-utf-7')

It returns the empty string.

[cl-parsons]

I edited the issue because it turns out that I was not testing it well...

[cl-parsons]

Links to the following issue in modoboa main repo :

modoboa/modoboa-webmail#227 (comment)