Flask's JSONIFY_PRETTYPRINT_REGULAR is deprecated, switch to app.json.compact

https://flask.palletsprojects.com/en/2.2.x/changes/#version-2-2-0

app.py

@@ -18,8 +18,8 @@ app.config.from_mapping(
     ENV='development' if appengine_info.DEBUG else 'PRODUCTION',
     CACHE_TYPE='SimpleCache',
     SECRET_KEY=util.read('flask_secret_key'),
-    JSONIFY_PRETTYPRINT_REGULAR=True,
 )
+app.json.compact = False
 app.url_map.converters['regex'] = flask_util.RegexConverter
 app.after_request(flask_util.default_modern_headers)
 app.register_error_handler(Exception, flask_util.handle_exception)