py3: replace os.sep with pycompat.ossep (part 1 of 4) os.sep returns unicodes on Python 3. We have pycompat.ossep which returns bytes. This patch is a part of 4 patch series which will replace all the occurrences of os.sep to pycompat.ossep

py3: replace os.pathsep with pycompat.ospathsep os.pathsep returns unicode on Python 3. We already have pycompat.ospathsep which return bytes on Python 3. This patch replaces all the occurrences of os.pathsep in the codebase (excluding tests) to pycompat.ospathsep.