My Python code started working after I changed on line.
Changing:
files_dct = {filename:fobj}
to:
files_dct = {('photo',(filename, fobj,'image/jpg'))}
Now it works. My conjecture about the need for different HTTP-headers was wrong. The working code has not changed the headers received by Django.
I must say, the Requests module documentation is very opaque!
I made this change based on a guess while reading the docs about sending multiple files. I can't say I understand what going on.
Please comment on the right way to do this.