partrt: test: Convert to python3
partrt: test: Convert to python3

* run 2to3 tool to automatically convert most of the py code to py3;
* manually fix some print statements that got extra paranthesis during
  the automatic conversion;
* remove unused 'io' import;
* add python3-specific shebang;
* add explicit conversion from bytes to string for 'stdout' in a couple
  of places:
-        for line in stdout.splitlines():
+        for line in stdout.decode('utf-8').splitlines():

Signed-off-by: Alexandru Avadanii <046230ef61405fd997a5cbd7cfcbca66da78c41e@enea.com>

OpenEneaLinux/rt-tools,OpenEneaLinux/rt-tools,OpenEneaLinux/rt-tools