[ADD] safe_eval: UNPACK_SEQUENCE and Exception

Allowing UNPACK_SEQUENCE allows the use of the "multi" assignation:
a, b = [1,2]
for a,b in items

openerp/tools/safe_eval.py

@@ -67,7 +67,7 @@ _SAFE_OPCODES = _EXPR_OPCODES.union(set(opmap[x] for x in [
     # New in Python 2.7 - http://bugs.python.org/issue4715 :
     'JUMP_IF_FALSE_OR_POP', 'JUMP_IF_TRUE_OR_POP', 'POP_JUMP_IF_FALSE',
     'POP_JUMP_IF_TRUE', 'SETUP_EXCEPT', 'END_FINALLY',
-    'LOAD_FAST', 'STORE_FAST', 'DELETE_FAST',
+    'LOAD_FAST', 'STORE_FAST', 'DELETE_FAST', 'UNPACK_SEQUENCE',
     'LOAD_GLOBAL', # Only allows access to restricted globals
     ] if x in opmap))
 
@@ -278,7 +278,8 @@ def safe_eval(expr, globals_dict=None, locals_dict=None, mode="eval", nocopy=Fal
                 'filter': filter,
                 'round': round,
                 'len': len,
-                'set' : set
+                'set' : set,
+                'Exception': Exception,
             }
     )
     try: