Latest update seems to have broken Mercurial

[David Monksfield]

Mercurial was working fine for me until my last Cywin update (yesterday).
I have Mercurial 5.5.1-1. I don't know enough about python to unpick this,
but it looks suspicious that there is a mixture of python2.7 and python3.8
in the traceback.

I now get this:

$ hg status
Traceback (most recent call last):
  File "/usr/bin/hg", line 43, in <module>
    dispatch.run()
  File "/usr/lib/python3.8/importlib/util.py", line 245, in __getattribute__
    self.__spec__.loader.exec_module(self)
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/usr/lib/python2.7/site-packages/mercurial/dispatch.py", line 22, in <module>
    from .i18n import _
  File "/usr/lib/python3.8/importlib/util.py", line 245, in __getattribute__
    self.__spec__.loader.exec_module(self)
  File "/usr/lib/python2.7/site-packages/mercurial/i18n.py", line 112, in <module>
    if _plain():
  File "/usr/lib/python2.7/site-packages/mercurial/i18n.py", line 104, in _plain
    b'HGPLAIN' not in encoding.environ
  File "/usr/lib/python3.8/importlib/util.py", line 245, in __getattribute__
    self.__spec__.loader.exec_module(self)
  File "/usr/lib/python2.7/site-packages/mercurial/encoding.py", line 40, in <module>
    charencode = policy.importmod('charencode')
  File "/usr/lib/python2.7/site-packages/mercurial/policy.py", line 116, in importmod
    mod = _importfrom(pn, mn)
  File "/usr/lib/python2.7/site-packages/mercurial/policy.py", line 67, in _importfrom
    pkg = __import__(pkgname, globals(), fakelocals, [modname], level=1)
  File "/usr/lib/python3.8/importlib/util.py", line 286, in create_module
    return self.loader.create_module(spec)
ImportError: dynamic module does not define module export function (PyInit_parsers)

Any help or suggestions would be appreciated.

Thanks,
David