Purge FTP index listing all Python versions from fastly cache (#1858)

Author: ewjoachim

downloads/models.py

@@ -276,6 +276,7 @@ def purge_fastly_download_pages(sender, instance, **kwargs):
         purge_url('/downloads/macos/')
         purge_url('/downloads/source/')
         purge_url('/downloads/windows/')
+        purge_url('/ftp/python/')
         if instance.get_version() is not None:
             purge_url(f'/ftp/python/{instance.get_version()}/')
         # See issue #584 for details