pretty-print JSON output

scripts/assets.py

@@ -4,10 +4,8 @@ import glob
 import json
 import os
 import pygame
-import random
 import re
 import sys
-from PIL import Image
 
 # The guide in tiles/guide.png is quite helpful.
 
@@ -248,7 +246,7 @@ def annotate_sprites(sprite_files, all_metadata):
         filename, all_metadata.get(filename))
     all_metadata[filename] = sprite_metadata
     with open('metadata.json', 'w') as f:
-      json.dump(all_metadata, f)
+      json.dump(all_metadata, f, sort_keys=True, indent=2)
     if quit:
       return