test_intl: add output message when (re)write of .mo file occurs

tests/test_intl.py

@@ -57,6 +57,7 @@ def _setup_intl(app_params):
 
             if not mo.exists() or mo.stat().st_mtime < po.stat().st_mtime:
                 # compile .mo file only if needed
+                print(f'# compiling .mo file {mo}')
                 write_mo(mo, read_po(po))