[PR PATCH] [Closed]: selftest/check_output: convert bytes to str for Python 3

[github at samba.org]

There's a closed pull request on the Samba Samba Github repository

selftest/check_output: convert bytes to str for Python 3
https://github.com/samba-team/samba/pull/150
Description: `BlackboxTestCase.check_output` will return bytes since it uses
`subprocess.communicate` underneath.
Convert expected string result to bytes for comparing.
This will be compatible for both Python 2 & 3.

Signed-off-by: Joe Guo <joeg at catalyst.net.nz>