@angonz thanks for bearing it with me. Issue reproduced and was fixed with the patch in Dockerfile.
Please change the changelog entry to below text only and remove the comment So that I can merge the change.
[Bugfix] Fix the docker image to allow media files to be served by uwsgi. (by @angonz)
If the media directory does not exist at the time that uwsgi is launched, the mapping to /media to serve media files will not be created.
See issue #69