Impacted versions

• Distribution: Ubuntu
• Codename: Focal (20.04.3)
• Arch: 64 Bits
• Database: PostgreSQL

Also tried with the following OSes, but stopped the installer after about 4~6 hours without any result:

• CentOS 7
• Debian 10
• Ubuntu 18.04 (latest version)

Steps to reproduce

Basic Ubuntu 20.04.3 server setup (or any of the above listes OSes), with SSH enabled. After setup is completed (XXXXX is a real existing domain):

$ time sudo python3 run.py --debug XXXXX
[...]
INFO: This is taking longer than usual. You might need to provide the dependency resolver with stricter constraints to reduce runtime. If you want to abort this run, you can press Ctrl + C to do so. To improve how pip performs, tell us what happened here: https://pip.pypa.io/surveys/backtracking
  Downloading modoboa-webmail-1.1.4.tar.gz (87 kB)
     |████████████████████████████████| 87 kB 3.0 MB/s
  Downloading modoboa-webmail-1.1.3.tar.gz (87 kB)
     |████████████████████████████████| 87 kB 4.5 MB/s
  Downloading modoboa-webmail-1.1.2.tar.gz (85 kB)
     |████████████████████████████████| 85 kB 4.3 MB/s
  Downloading modoboa-webmail-1.1.1.tar.gz (84 kB)
     |████████████████████████████████| 84 kB 3.8 MB/s
ERROR: Exception:
Traceback (most recent call last):
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_internal/cli/base_command.py", line 173, in _main
    status = self.run(options, args)
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_internal/cli/req_command.py", line 203, in wrapper
    return func(self, options, args)
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_internal/commands/install.py", line 315, in run
    requirement_set = resolver.resolve(
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_internal/resolution/resolvelib/resolver.py", line 94, in resolve
    result = self._result = resolver.resolve(
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_vendor/resolvelib/resolvers.py", line 472, in resolve
    state = resolution.resolve(requirements, max_rounds=max_rounds)
  File "/srv/modoboa/env/lib/python3.8/site-packages/pip/_vendor/resolvelib/resolvers.py", line 383, in resolve
    raise ResolutionTooDeep(max_rounds)
pip._vendor.resolvelib.resolvers.ResolutionTooDeep: 2000000
Traceback (most recent call last):
  File "/srv/modoboa/env/bin/modoboa-admin.py", line 4, in <module>
    from modoboa.core.commands import handle_command_line
  File "/srv/modoboa/env/lib/python3.8/site-packages/modoboa/core/__init__.py", line 3, in <module>
    from django.core.urlresolvers import reverse
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/core/urlresolvers.py", line 16, in <module>
    from django.http import Http404
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/http/__init__.py", line 4, in <module>
    from django.http.response import (
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/http/response.py", line 13, in <module>
    from django.core.serializers.json import DjangoJSONEncoder
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/core/serializers/__init__.py", line 23, in <module>
    from django.core.serializers.base import SerializerDoesNotExist
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/core/serializers/base.py", line 6, in <module>
    from django.db import models
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/db/models/__init__.py", line 6, in <module>
    from django.db.models.query import Q, QuerySet, Prefetch  # NOQA
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/db/models/query.py", line 13, in <module>
    from django.db.models.fields import AutoField, Empty, FieldDoesNotExist
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/db/models/fields/__init__.py", line 18, in <module>
    from django import forms
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/forms/__init__.py", line 6, in <module>
    from django.forms.fields import *  # NOQA
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/forms/fields.py", line 18, in <module>
    from django.forms.utils import from_current_timezone, to_current_timezone
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/forms/utils.py", line 15, in <module>
    from django.utils.html import format_html, format_html_join, escape
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/utils/html.py", line 16, in <module>
    from .html_parser import HTMLParser, HTMLParseError
  File "/srv/modoboa/env/lib/python3.8/site-packages/django/utils/html_parser.py", line 12, in <module>
    HTMLParseError = _html_parser.HTMLParseError
AttributeError: module 'html.parser' has no attribute 'HTMLParseError'
None

real    1562m4.217s
user    1557m54.697s
sys     1m13.077s

Especially this line:

pip._vendor.resolvelib.resolvers.ResolutionTooDeep: 2000000

Expected behavior

Installation finishes.

Notes

• I did this installation on a Debian 10 about 5 months ago, and it finished pretty fast.
• Currently this does not work on any of the tested OS versions, because pip is installed in the modoboa environment at the latest version which uses the new dependency resolver.
• I tried setting ~modoboa/env/pip.conf (aka $VIRTUAL_ENV/pip.conf) with different values, but currently I didn’t find a working fix/hack to make the installer work. This idea was based on several “stackoverflow suggestions”. Especially use-deprecated=legacy-resolver did not work, actually it fails pretty fast.