Fixed OSError "No such file or directory: None" and make IOError consistent. The None error occurs when the current working directory is no longer available, e.g. because it was removed in another shell.

#!/bin/sh

hg init
mkfifo p

hg serve --stdio < p &
P=$!
(echo lock; echo addchangegroup; sleep 5) > p &
Q=$!
sleep 3
kill -HUP $P
wait
ls .hg