RuntimeError at /api/projects/project/2
You called this URL via PATCH, but the URL doesn't end in a slash and you have APPEND_SLASH set. Django can't redirect to the slash URL while maintaining PATCH data. Change your form to point to localhost:8000/api/projects/project/2/ (note the trailing slash), or set APPEND_SLASH=False in your Django settings.
RuntimeError at /api/projects/project/2 You called this URL via PATCH, but the URL doesn't end in a slash and you have APPEND_SLASH set. Django can't redirect to the slash URL while maintaining PATCH data. Change your form to point to localhost:8000/api/projects/project/2/ (note the trailing slash), or set APPEND_SLASH=False in your Django settings.