Add note explaining non-standard import style.

lib/python/AccessControl/Owned.py

@@ -31,10 +31,10 @@ from AccessControl.Permissions import take_ownership
 from AccessControl.requestmethod import requestmethod
 from AccessControl.SecurityInfo import ClassSecurityInfo
 from AccessControl.SecurityManagement import getSecurityManager
+# avoid importing 'emergency_user' / 'nobody'  before set
 from AccessControl import SpecialUsers as SU
 from AccessControl.unauthorized import Unauthorized
 
-
 UnownableOwner=[]
 def ownableFilter(self):
     _owner = aq_get(self, '_owner', None, 1)