Single Tree setup with MEDIA_PREFIX_TREE=true does not create media directory

[strombringer]

Environment:

• Existing Gramps tree on Windows Desktop
• New installation of GrampsWeb in docker stack,
  • no tree imported
  • MEDIA_PREFIX_TREE=true
• Existing family tree (no media files) synced from Desktop to Web

Steps to reproduce:

• Gramps Web -> Media List -> New Media Object -> Select photo -> Add

Expected:

• Media file is added

Actual:

• "Error: NOT FOUND" is displayed in the bottom left

Logs:

[2024-05-01 13:30:24 +0000] [15] [ERROR] Error handling request /api/media/
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/dist-packages/gunicorn/workers/sync.py", line 135, in handle
    self.handle_request(listener, req, client, addr)
  File "/usr/local/lib/python3.11/dist-packages/gunicorn/workers/sync.py", line 178, in handle_request
    respiter = self.wsgi(environ, resp.start_response)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 1488, in __call__
    return self.wsgi_app(environ, start_response)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 1466, in wsgi_app
    response = self.handle_exception(e)
               ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 1463, in wsgi_app
    response = self.full_dispatch_request()
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 872, in full_dispatch_request
    rv = self.handle_user_exception(e)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 870, in full_dispatch_request
    rv = self.dispatch_request()
         ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/app.py", line 855, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)  # type: ignore[no-any-return]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/gramps_webapi/api/auth.py", line 44, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/views.py", line 110, in view
    return current_app.ensure_sync(self.dispatch_request)(**kwargs)  # type: ignore[no-any-return]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/flask/views.py", line 191, in dispatch_request
    return current_app.ensure_sync(meth)(**kwargs)  # type: ignore[no-any-return]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/gramps_webapi/api/resources/media.py", line 83, in post
    check_quota_media(to_add=size)
  File "/usr/local/lib/python3.11/dist-packages/gramps_webapi/api/media.py", line 371, in check_quota_media
    update_usage_media(tree=tree)
  File "/usr/local/lib/python3.11/dist-packages/gramps_webapi/api/media.py", line 360, in update_usage_media
    usage_media = media_handler.get_media_size(db_handle=db_handle)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/gramps_webapi/api/media.py", line 151, in get_media_size
    raise ValueError(f"Directory {self.base_dir} does not exist")
ValueError: Directory /app/media/dfb22cac-3453-433c-b7a9-b75aecd90c1e does not exist

When I manually create the folder in the filesystem, everything works as expected.