py3: have pycompat.ospathsep and pycompat.ossep We needed bytes version of os.sep and os.pathsep in py3 as they return unicodes.

py3: add a bytes version of os.name os.name returns unicodes on py3. Most of our checks are like os.name == 'nt' Because of the transformer, on the right hand side we have b'nt'. The condition will never satisfy even if os.name returns 'nt' as that will be an unicode. We either need to encode every occurence of os.name or have a new variable which is much cleaner. Now we have pycompat.osname. There are around 53 occurences of os.name in the codebase which needs to be replaced by pycompat.osname to support Python 3.

py3: make util.datapath a bytes variable In this patch we make util.datapath a bytes variable, but we have to pass a unicode to gettext.translation otherwise it will cry. Used pycompat.fsdecode() to decode it back to unicode as it was converted to bytes using pycompat.fsencode().

py3: add os.fsdecode() as pycompat.fsdecode() We need to use os.fsdecode() but this was not present in Python 2. So added the function in pycompat.py