raise on failed token creation

the logic was there but at the wrong indentation level
causing it to only raise sometimes

jupyterhub/app.py

@@ -1876,7 +1876,7 @@ class JupyterHub(Application):
                         # don't allow bad tokens to create users
                         db.delete(obj)
                         db.commit()
-                        raise
+                    raise
             else:
                 self.log.debug("Not duplicating token %s", orm_token)
         db.commit()