Improve error reporting from stash

Differential Revision: https://phabricator.services.mozilla.com/D176170

resource-timing/resources/fake_responses.py

@@ -13,8 +13,8 @@ def main(request, response):
     date = request.GET.first(b"date", b"")
     modified = request.headers.get(b"If-Modified-Since", None)
     url = request.GET.first(b"url", None)
-    response.headers.set(b"Access-Control-Allow-Origin", b"*");
-    response.headers.set(b"Timing-Allow-Origin", b"*");
+    response.headers.set(b"Access-Control-Allow-Origin", b"*")
+    response.headers.set(b"Timing-Allow-Origin", b"*")
     if tag:
         response.headers.set(b"ETag", b'"%s"' % tag)
     elif date:
@@ -30,6 +30,7 @@ def main(request, response):
         response.headers.set(b"Content-Type", b"text/javascript")
         with open(filepath, 'rb') as f:
             filedata = f.read()
+
         return filedata
 
     if ((match is not None and match == tag) or

tools/wptserve/wptserve/stash.py

@@ -194,7 +194,11 @@ def _wrap_key(self, key, path):
         if isinstance(key, bytes):
             # UUIDs are within the ASCII charset.
             key = key.decode('ascii')
-        return (isomorphic_encode(path), uuid.UUID(key).bytes)
+        try:
+            my_uuid = uuid.UUID(key).bytes
+        except ValueError as e:
+            raise ValueError(f"""Invalid UUID "{key}" used as stash key""") from e
+        return (isomorphic_encode(path), my_uuid)
 
     def put(self, key, value, path=None):
         """Place a value in the shared stash.