Occasional server errors from password reset

[rebeccacremona]

Why does this still happen sometimes?

Internal Server Error: /password/reset/<redacted>/set-password

KeyError at /password/reset/<redacted>/set-password
'_password_reset_token'

Request Method: POST
Request URL: https://perma.cc/password/reset/NjIwNTY/set-password
Django Version: 2.2.24
Python Executable: /usr/bin/uwsgi-core
Python Version: 3.7.3
Server time: Tue, 26 Oct 2021 20:35:58 +0000

Traceback:  

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/core/handlers/exception.py" in inner
  34.             response = get_response(request)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  115.                 response = self.process_exception_by_middleware(e, request)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  113.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/views/generic/base.py" in view
  71.             return self.dispatch(request, *args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/utils/decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/views/decorators/debug.py" in sensitive_post_parameters_wrapper
  76.             return view(request, *args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/utils/decorators.py" in _wrapper
  45.         return bound_method(*args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  44.         response = view_func(request, *args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/contrib/auth/views.py" in dispatch
  270.                     return super().dispatch(*args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/views/generic/base.py" in dispatch
  97.         return handler(request, *args, **kwargs)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/views/generic/edit.py" in post
  142.             return self.form_valid(form)

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/contrib/auth/views.py" in form_valid
  300.         del self.request.session[INTERNAL_RESET_SESSION_TOKEN]

File "/usr/local/share/perma/perma_web/.venv/lib/python3.7/site-packages/django/contrib/sessions/backends/base.py" in __delitem__
  61.         del self._session[key]