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
python -c 'print "confuse str.splitlines\nembedded\rnewline"' > a
hg ci -Ama -d '1 0'
echo clean diff >> a
hg ci -mb -d '2 0'
hg diff -r0 -r1