How to Update a Testlead field for a Issue

[abhinav-4952]

issue.update(testlead={'name':'sai_kammari'})

I've been using the above code to update test lead value for Jira issue.But I am getting the following error:-

response text = {"errorMessages":[],"errors":{"testlead":"Field 'testlead' cannot be set. It is not on the appropriate screen, or unknown."}}

[Nic Brough -Adaptavist-]

This error means what it says - the field you are trying to set is not on the edit screen for the issue.  However, this might also be caused by the user you are using not having access to edit (because they are not logged in, or don't have edit permission)