qapi: Adapt to moved location of 'maketrans' function in py3

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20180116134217.8725-6-berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

scripts/qapi.py

@@ -1734,7 +1734,10 @@ def c_enum_const(type_name, const_name, prefix=None):
         type_name = prefix
     return camel_to_upper(type_name) + '_' + c_name(const_name, False).upper()
 
-c_name_trans = string.maketrans('.-', '__')
+if hasattr(str, 'maketrans'):
+    c_name_trans = str.maketrans('.-', '__')
+else:
+    c_name_trans = string.maketrans('.-', '__')
 
 
 # Map @name to a valid C identifier.