Use 'except ... as' syntax

This syntax works on Python 2.6 through 3.x.  lib/ansible/module_utils
(and lib/ansible/modules) need to support Python 2.4, so I didn't touch
those.

lib/ansible/plugins/lookup/sequence.py

@@ -186,7 +186,7 @@ class LookupModule(LookupBase):
                 try:
                     if not self.parse_simple_args(term):
                         self.parse_kv_args(parse_kv(term))
-                except Exception, e:
+                except Exception as e:
                     raise AnsibleError("unknown error parsing with_sequence arguments: %r. Error was: %s" % (term, e))
 
                 self.sanity_check()