obsync fail when grantee are like AllUsers

[guilhem]

<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://s3.amazonaws.com/doc/2006-03-01/" xsi:type="Group"><URI>http://acs.amazonaws.com/groups/global/AllUsers</URI></Grantee>

Traceback (most recent call last):
File "/usr/bin/obsync", line 1226, in <module>
src_acl = src.get_acl(sobj)
File "/usr/bin/obsync", line 678, in get_acl
return LocalAcl.from_xml(obj.name, acl_xml)
File "/usr/bin/obsync", line 577, in from_xml
acl_policy = AclPolicy.from_xml(xml)
  File "/usr/bin/obsync", line 394, in from_xml
    user_id = grantee.find("{%s}ID" % NS).text
AttributeError: 'NoneType' object has no attribute 'text'
ERROR TYPE: unknown, ORIGIN: source