Use json for error response of REST api

This uses application/json for error response too. With this, all REST
api return application/json except 404 error (we can't use
@blueprint.errorhandler(404) for now) and ItemDownloadView
(ItemDownloadView uses "Content-Type" as downloaded data type).

src/bepasty/apis/rest.py

@@ -26,17 +26,22 @@
 # "/lodgeit/" in the same blueprint and there is no way to exclude
 # from using the same error handler ("/lodgeit/" is not REST api).
 def rest_errorhandler(func):
+    def error_message(description, code):
+        return jsonify({
+            'error': {'code': code, 'message': description},
+        }), code
+
     def handler(*args, **kwargs):
         try:
             return func(*args, **kwargs)
         except HTTPException as exc:
-            return exc.description, exc.code
+            return error_message(exc.description, exc.code)
         except Exception:
             if current_app.propagate_exceptions:
                 # if testing/debug mode, re-raise
                 raise
             exc = InternalServerError()
-            return exc.description, exc.code
+            return error_message(exc.description, exc.code)
 
     return handler
 

src/bepasty/tests/test_rest_server.py

@@ -160,7 +160,9 @@ def check_response(response, code, ftype='application/json', check_data=True):
 
 
 def check_err_response(response, code, check_data=True):
-    check_response(response, code, 'text/html; charset=utf-8', check_data)
+    check_response(response, code, check_data=check_data)
+    if check_data:
+        assert code == response.json['error']['code']
     # check if doesn't have html tag
     assert not re.match(r'<.+>', response.data.decode())