image-fuzzer: Use OSerror.strerror instead of tuple subscript

OSError can't be used like a tuple on Python 3, so change the
code to use `e.sterror` instead of `e[1]`.

Reported-by: John Snow <jsnow@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20191021214117.18091-1-ehabkost@redhat.com
Message-Id: <20191021214117.18091-1-ehabkost@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed