[Python-modules-team] Bug#960537: python3-html5lib: DeprecationWarning in collections import (will be failure with python3.9)

[Scott Kitterman]

Package: python3-html5lib
Version: 1.0.1-3
Severity: normal

Currently with python3.7 or 3.8:
DeprecationWarning: Using or importing the ABCs from 'collections' instead of
from 'collections.abc' is deprecated, and in 3.9 it will stop working
  from collections import Mapping

When we get python3.9 it'll be:

Python 3.9.0a2+ (heads/master:b0d4949, Dec 20 2019, 11:38:30)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import html5lib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/__init__.py", line 25, in <module>
    from .html5parser import HTMLParser, parse, parseFragment
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/html5parser.py", line 8, in <module>
    from . import _tokenizer
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/_tokenizer.py", line 16, in <module>
    from ._trie import Trie
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/_trie/__init__.py", line 3, in <module>
    from .py import Trie as PyTrie
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/_trie/py.py", line 6, in <module>
    from ._base import Trie as ABCTrie
  File "/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/site-packages/html5lib/_trie/_base.py", line 3, in <module>
    from collections import Mapping
ImportError: cannot import name 'Mapping' from 'collections' (/home/pi/.pyenv/versions/3.9-dev/lib/python3.9/collections/__init__.py)

I noticed this because python-bleach is looking into updating their
vendored copy (we don't use it) [1].  This change has been in html5lib
for some time [2], but with no release coming, I think we should fix it in
Debian.

Scott K

[1] https://patch-diff.githubusercontent.com/raw/mozilla/bleach/pull/533.diff
[2] https://github.com/html5lib/html5lib-python/blob/master/html5lib/_trie/_base.py#L3