Sorry for the spam, but I also managed to get something slightly different (doesn't seem to be reproducible easily though):
--8<---------------cut here---------------start------------->8--- scheme@(guix-user)> ,m (shepherd service) scheme@(shepherd service)> (make-forkexec-constructor (list "/gnu/store/qyz1bncxlkxv44c03sva2akfsyqzkzh5-nfs-utils-2.4.2/sbin/rpc.mountd" "--debug" "all")) $1 = #<procedure 7f5f7e17e600 at shepherd/service.scm:930:8 args> scheme@(shepherd service)> ($1) $2 = 920 scheme@(shepherd service)> error in finalization thread: Bad file descriptor warning: 'waitpid' -1 failed unexpectedly: No child processes --8<---------------cut here---------------end--------------->8---
