Reduce noise when extracting and updating catalogs

We omit the header as they are not filled nor used.
We do not put location in comment as they are changing too often.
We ignore the obsolete translations.

issue8160
review47871002

setup.py

@@ -18,11 +18,23 @@ args = {}
 try:
     from babel.messages import frontend as babel
 
+    class extract_messages(babel.extract_messages):
+        def initialize_options(self):
+            super().initialize_options()
+            self.omit_header = True
+            self.no_location = True
+
+    class update_catalog(babel.update_catalog):
+        def initialize_options(self):
+            super().initialize_options()
+            self.omit_header = True
+            self.ignore_obsolete = True
+
     args['cmdclass'] = {
         'compile_catalog': babel.compile_catalog,
-        'extract_messages': babel.extract_messages,
+        'extract_messages': extract_messages,
         'init_catalog': babel.init_catalog,
-        'update_catalog': babel.update_catalog,
+        'update_catalog': update_catalog,
         }
 
     args['message_extractors'] = {