[Python] Python Wagtail crashes 6.3.1 "Streamfield object has no attribute 'bind_to_model'

(Edited 4pm today based on comments given below.)

While updating an old Wagtail website to the current version, I encounter this error, in admin/panels/group.py line 74:

AttributeError: 'StreamField' object has no attribute 'bind_to_model'

Since this is apparently in the Wagtail software as distributed, I am quite confused.


The full traceback is as follows:

Exception in thread django-main-thread:
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 1041, in _bootstrap_inner
self.run()
~~~~~~~~^^
File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 992, in run
self._target(*self._args, **self._kwargs)
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/utils/autoreload.py", line 64, in wrapper
fn(*args, **kwargs)
~~^^^^^^^^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/management/commands/runserver.py", line 134, in inner_run
self.check(display_num_errors=True)
~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/management/base.py", line 486, in check
all_issues = checks.run_checks(
app_configs=app_configs,
...<2 lines>...
databases=databases,
)
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/checks/registry.py", line 88, in run_checks
new_errors = check(app_configs=app_configs, databases=databases)
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/checks.py", line 69, in get_form_class_check
edit_handler = cls.get_edit_handler()
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/utils/decorators.py", line 54, in __call__
return self.value
^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/utils/functional.py", line 47, in __get__
res = instance.__dict__[self.name] = self.func(instance)
~~~~~~~~~^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/utils/decorators.py", line 50, in value
return self.fn(self.cls)
~~~~~~~^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/page_utils.py", line 73, in _get_page_edit_handler
return edit_handler.bind_to_model(cls)
~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/base.py", line 146, in bind_to_model
new.on_model_bound()
~~~~~~~~~~~~~~~~~~^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/group.py", line 74, in on_model_bound
self.children = [child.bind_to_model(self.model) for child in self.children]
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/base.py", line 146, in bind_to_model
new.on_model_bound()
~~~~~~~~~~~~~~~~~~^^
File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/group.py", line 74, in on_model_bound
self.children = [child.bind_to_model(self.model) for child in self.children]
^^^^^^^^^^^^^^^^^^^
AttributeError: 'StreamField' object has no attribute 'bind_to_model'

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