AttributeError: 'ClientResponse' object has no attribute 'request'

Sentry Issue: [LMS-1EP](https://hypothesis.sentry.io/issues/6816394647/?referrer=github_integration)

```
FileNotFoundInCourse: None
File "lms/views/api/blackboard/files.py", line 84, in via_url
raise FileNotFoundInCourse( # noqa: TRY301

ValidationError: {'results': ['Missing data for required field.']}
File "lms/validation/_base.py", line 141, in parse
return self.load(self._response, *args, **kwargs)

AttributeError: 'ClientResponse' object has no attribute 'request'
(20 additional frame(s) were not displayed)
...
File "lms/services/blackboard_api/client.py", line 250, in _get_all_folders_files
results.extend(self._get_all_folders_files(course_id, folder_files))
File "lms/services/blackboard_api/client.py", line 250, in _get_all_folders_files
results.extend(self._get_all_folders_files(course_id, folder_files))
File "lms/services/blackboard_api/client.py", line 246, in _get_all_folders_files
folder_files = self._get_all_following_pages(
File "lms/services/blackboard_api/client.py", line 217, in _get_all_following_pages
results = schema(response).parse()
File "lms/validation/_base.py", line 143, in parse
request = self._response.request if self._response is not None else None
```