inst.reason isn't alway in the form (errno, strerror)
urllib2.urlopen("foobar://foo") is an example
where inst.reason is a string
fix issue383
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i