py3: add os.getcwdb() to have bytes path Following the behaviour of Python 3, os.getcwd() return unicodes. We need bytes version as path variables are bytes in UNIX. Python 3 has os.getcwdb() which returns current working directory in bytes. Like rest of the things there in pycompat, like osname, ossep, we need to rewrite every instance of os.getcwd to pycompat.getcwd to make them work correctly on Python 3.