Asana API querying by assignee_status
You actually can't filter by assignee_status at all - if you pass the parameter it is silently ignored. We could change it so that unrecognized parameters result in errors, which would help make this clearer.
When Querying just for tasks that are marked for today in python: 
client.tasks.find_all({ 'assignee_status':'upcoming','workspace': 000000000,'assignee':'me' ,'completed_since':'now'}, page_size=100)
I get a response of all tasks the same as if I would not have included assignee_status
client.tasks.find_all({'workspace': 000000000,'assignee':'me' ,'completed_since':'now'}, page_size=100)
The workspace space has around 5 task that are marked for today.
Thank you,
Greg