def rel_posix_to_abs_local(host, path, environ=None):
    if environ is None:
        environ = os.environ
    if path.startswith('/'):
        path = path[1:]
    root = path_for_host(host, environ)
    return os.path.join(root, *path.split('/'))
Convert a POSIX path to the current system's format and prepend the
dataset/ETHPy150Open Yelp/mrjob/tests/mockssh.py/rel_posix_to_abs_local