Hmm...  Looks like a unified diff to me...
The text leading up to this was:
--------------------------
|--- x.c	2020-05-07 16:51:55.080437829 +0200
|+++ x.c	2020-05-07 16:51:23.850218201 +0200
--------------------------
Patching file x.c using Plan A...
Hunk #1 failed at 812.
1 out of 1 hunks failed
done