Fail to build for Python 3.10.0a4+

[nicobo]

AttributeError: module 'collections' has no attribute 'MutableSet' when building against python:nightly

Full error log from https://travis-ci.com/github/nicolabs/nicobot/jobs/473553168 :

$ source ~/virtualenv/pythonnightly/bin/activate
$ python --version
Python 3.10.0a4+
$ pip --version
pip 20.3.3 from /home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/pip (python 3.10)
install.1
0.96s$ python setup.py build
install.2
44.82s$ pip install -r requirements-build.txt -r requirements-runtime.txt
0.16s$ python -m unittest discover -s tests
E
======================================================================
ERROR: test_askbot (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_askbot
Traceback (most recent call last):
  File "/opt/python/3.10-dev/lib/python3.10/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/opt/python/3.10-dev/lib/python3.10/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/home/travis/build/nicolabs/nicobot/tests/test_askbot.py", line 6, in <module>
    from nicobot.askbot import AskBot
  File "/home/travis/build/nicolabs/nicobot/nicobot/__init__.py", line 2, in <module>
    from .bot import Bot
  File "/home/travis/build/nicolabs/nicobot/nicobot/bot.py", line 11, in <module>
    from .jabber import JabberChatter
  File "/home/travis/build/nicolabs/nicobot/nicobot/jabber.py", line 12, in <module>
    import slixmpp_omemo
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp_omemo/__init__.py", line 21, in <module>
    from slixmpp.plugins.xep_0060.stanza import Items, EventItems
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0060/__init__.py", line 11, in <module>
    from slixmpp.plugins.xep_0060.pubsub import XEP_0060
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0060/pubsub.py", line 15, in <module>
    from slixmpp.plugins.xep_0060 import stanza
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0060/stanza/__init__.py", line 9, in <module>
    from slixmpp.plugins.xep_0060.stanza.pubsub import *
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0060/stanza/pubsub.py", line 11, in <module>
    from slixmpp.plugins import xep_0004
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0004/__init__.py", line 11, in <module>
    from slixmpp.plugins.xep_0004.stanza import Form
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0004/stanza/__init__.py", line 10, in <module>
    from slixmpp.plugins.xep_0004.stanza.form import Form
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/plugins/xep_0004/stanza/form.py", line 12, in <module>
    from slixmpp.thirdparty import OrderedSet
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/thirdparty/__init__.py", line 7, in <module>
    from slixmpp.thirdparty.orderedset import OrderedSet
  File "/home/travis/virtualenv/python3.10-dev/lib/python3.10/site-packages/slixmpp/thirdparty/orderedset.py", line 25, in <module>
    class OrderedSet(collections.MutableSet):
AttributeError: module 'collections' has no attribute 'MutableSet'