io/wait: wait_readable/writable working different than IO.select when descriptor not open
Coming from this pending issue:
Gist of it:
f = IO.popen("/bin/sh","r+")
f.wait_writable #=> IOError: not opened for writing
IO.select(nil,[f],nil,10) #=> no error
The way I see it, it should have the same behaviour, i.e. either IO.select should complain, or wait_writable should just return nil.