ValueError: Invalid isoformat string on Python 3.10

[antoinemacia]

Getting the following error from the client on Python 3.10

2025-10-27 22:43:12,387: ERROR/ForkPoolWorker-31] Error parsing environment document
Traceback (most recent call last):
  File "/opt/venv/lib/python3.10/site-packages/flagsmith/flagsmith.py", line 304, in update_environment
    map_environment_document_to_environment_updated_at(
  File "/opt/venv/lib/python3.10/site-packages/flagsmith/mappers.py", line 41, in map_environment_document_to_environment_updated_at
    updated_at := datetime.fromisoformat(environment_document["updated_at"])
ValueError: Invalid isoformat string: '2025-10-22T23:10:57.624046Z'

What's weird is the client still somewhat works, but also gets in this endless retry logic of refetching the environment document - this has ramped up our usage to 50k fetch per day on a non-production server, and has got us over the limit

I believe this could be related to this which we're trying to upgrade to, but the pyproject.toml should be updated to deprecate python 3.10