code gen: Be more robust to dirty hashes.

.gitignore

@@ -93,3 +93,6 @@ Release_Win32/
 Release_x64/
 TestResults.qpa
 .idea/
+
+# Any temporary files will confuse code generation.
+!scripts/code_generation_hashes/*

scripts/run_code_generation.py

@@ -182,7 +182,10 @@ def load_hashes():
     for file in os.listdir(hash_dir):
         hash_fname = os.path.join(hash_dir, file)
         with open(hash_fname) as hash_file:
-            hashes[file] = json.load(open(hash_fname))
+            try:
+                hashes[file] = json.load(hash_file)
+            except ValueError:
+                raise Exception("Could not decode JSON from %s" % file)
     return hashes