Fix backend.

examples/react-spa-app/backend/main.py

@@ -14,7 +14,7 @@
 
 import functions_framework
 import os
-import requests
+import sys
 from google.auth.transport import requests
 from google.oauth2 import id_token
 from flask import abort
@@ -45,13 +45,14 @@ def validate_iap_jwt(iap_jwt, expected_audience):
         )
         return (decoded_jwt["sub"], decoded_jwt["email"], "")
     except Exception as e:
+        print(f"**ERROR: JWT validation error {e}**", file=sys.stderr)
         return (None, None, f"**ERROR: JWT validation error {e}**")
 
 @functions_framework.http
 def hello_function(request):
   if os.getenv("IAP_AUDIENCE"):
     ret = validate_iap_jwt(request.headers.get("x-goog-iap-jwt-assertion"), os.getenv("IAP_AUDIENCE"))
-    if ret[0] == None:
+    if not ret[0]:
       abort(403)
     return "Hello World: %s" % (ret[0])
   return 'Hello World'