Try to fix exception propagation from REST api

Author: ponyisi

servicex_app/servicex_app/__init__.py

@@ -294,7 +294,7 @@ def b64decode(text):  # needed for python selection decoding to web page.
             app.logger.error("Supplied Transformer Persistent Volume Claim Doesn't exist")
             sys.exit(-1)
 
-        api = Api(app)
+        api = Api(app, errors=Flask.errorhandler)
 
         # ensure the instance folder exists
         try: