--- a/src/pyams_utils/interfaces/__init__.py	Wed Jun 12 20:06:45 2019 +0200
+++ b/src/pyams_utils/interfaces/__init__.py	Fri Jun 14 12:41:06 2019 +0200
@@ -10,18 +10,18 @@
 # FOR A PARTICULAR PURPOSE.
 #
 
+"""PyAMS_utils interfaces module
+
+This module defines several generic constants and interfaces.
+It is also used to provide translations to common zope.schema exceptions.
+"""
+
 __docformat__ = 'restructuredtext'
 
-
-# import standard library
-
-# import interfaces
-from zope.schema.interfaces import WrongContainedType, NotUnique, SchemaNotFullyImplemented, SchemaNotProvided, \
-    InvalidURI, InvalidId, InvalidDottedName, Unbound, RequiredMissing, WrongType, TooBig, TooSmall, TooLong, \
-    TooShort, InvalidValue, ConstraintNotSatisfied, NotAContainer, NotAnIterator
-
-# import packages
 from zope.interface import Interface
+from zope.schema.interfaces import ConstraintNotSatisfied, InvalidDottedName, InvalidId, InvalidURI, InvalidValue, \
+    NotAContainer, NotAnIterator, NotUnique, RequiredMissing, SchemaNotFullyImplemented, SchemaNotProvided, TooBig, \
+    TooLong, TooShort, TooSmall, Unbound, WrongContainedType, WrongType
 
 from pyams_utils import _
 
@@ -56,7 +56,7 @@
 #
 
 FORBIDDEN_PERMISSION = 'system.forbidden'
-'''Custom permission which is never granted to any user'''
+'''Custom permission which is never granted to any user, even system manager'''
 
 PUBLIC_PERMISSION = 'public'
 '''Public permission which is granted to every principal'''