Got the answer from CUPS upstream and it seems to be a glibc bug:
"OK, looking at the glibc code, the only way we hit this assert is if args.err is not getting set by the child process. But I can't see how that would happen since __spawni_child always sets a value 0 or errno.
Got the answer from CUPS upstream and it seems to be a glibc bug:
"OK, looking at the glibc code, the only way we hit this assert is if args.err is not getting set by the child process. But I can't see how that would happen since __spawni_child always sets a value 0 or errno.
Right now this doesn't look like us..."
Adding glibc task ...