Set the JSON charset according to spec

See https://spaceapi.io/provide-an-endpoint/ for details

Author: penguineer

src/app.py

@@ -96,7 +96,7 @@ def initialize(self, observer):
         self.observer = observer
 
     def get(self):
-        self.set_header("Content-Type", "application/json")
+        self.set_header("Content-Type", "application/json; charset=utf-8")
         self.write(json.dumps(self.observer.get_space_api_entry(), indent=4))
         self.finish()