Поскольку версия shutil поддерживает необязательную группу, я копирую и вставляю код в мой проект Python2.
https://hg.python.org/cpython/file/tip/Lib/shutil.py#l1010
def chown(path, user=None, group=None):
"""Change owner user and group of the given path.
user and group can be the uid/gid or the user/group names, and in that case,
they are converted to their respective uid/gid.
"""
if user is None and group is None:
raise ValueError("user and/or group must be set")
_user = user
_group = group
# -1 means don't change it
if user is None:
_user = -1
# user can either be an int (the uid) or a string (the system username)
elif isinstance(user, basestring):
_user = _get_uid(user)
if _user is None:
raise LookupError("no such user: {!r}".format(user))
if group is None:
_group = -1
elif not isinstance(group, int):
_group = _get_gid(group)
if _group is None:
raise LookupError("no such group: {!r}".format(group))
os.chown(path, _user, _group)