Restore an exception.

It is intended to raise even when running in optimised mode. The intent of
that change was to allow interpreter to detect the last elif is not
expected to be needed (although it is not known to make such deductions
currently). If only python had a deeper "enum" notion...
This (very) partially reverts f32e9120.

neo/master/handlers/identification.py

@@ -65,7 +65,7 @@ class IdentificationHandler(MasterHandler):
             handler = app.administration_handler
             human_readable_node_type = 'n admin '
         else:
-            assert False, node_type
+            raise NotImplementedError(node_type)
 
         while not app.isValidUUID(uuid, address):
             uuid = app.getNewUUID(node_type)