A more general change to our authentication code caused setting --authentication-file=/proc/self/fd/3 to no longer to work.
A use case is eg:
Created attachment 14991 [details]
patch for 4.10 cherry-picked from master
Please select for 4.10. (It might also be good for 4.9, I've not checked yet).
Pushed to autobuild-v4-10-test.
(In reply to Karolin Seeger from comment #3)
Pushed again to autobuild-v4-10-test.
Pushed to v4-10-test.
Closing out bug report.