Exception Value: 'FileMetadata' object is not subscriptable with Dropbox backend

[math-a3k]

Using:

Django==2.2.1
django-storages==1.7.1
dropbox==9.3.0
wagtail==2.5.1

After uploading a document, the document is uploaded to Dropbox correctly, but when trying to retrieve the file it shows the following traceback:

Traceback:

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/django/core/handlers/exception.py" in inner
  34.             response = get_response(request)

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  115.                 response = self.process_exception_by_middleware(e, request)

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/django/core/handlers/base.py" in _get_response
  113.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/wagtail/documents/views/serve.py" in serve
  70.         response['Content-Length'] = doc.file.size

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/django/db/models/fields/files.py" in size
  69.         return self.storage.size(self.name)

File "/home/bot/code/conuruinca/venv/lib/python3.7/site-packages/storages/backends/dropbox.py" in size
  93.         return metadata['bytes']

Exception Type: TypeError at /documents/1/Tips
Exception Value: 'FileMetadata' object is not subscriptable

[jschneier]

Fixed by #724.