io: fix path_msg on python2

io: fix path_msg on python2

We get the binary representation here on both python 2 and 3,
but on 2 we really don't need to do any decoding since we must
print it as 'str'. Decoding also fails if the input is valid
UTF-8, which seems strange, but even if it worked we actually
don't want unicode objects here to print, we'd have to encode
them again to print.

Reported-by: Henninger Henningstone <henningstone@gmx.de>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Rob Browning <rlb@defaultvalue.org>
Tested-by: Rob Browning <rlb@defaultvalue.org>