Unable to open attachments added with python-asana

I have created a milestone and added subtasks to it. I am trying to attach a .msg file to be downloaded and used by outlook. I can attach the file but it will not open due to a permissions issue. If I manually add the file as an attachment in my project it works just fine. Any suggestions?
I am unsure what content_types are available and maybe this is part of the issue. Below is a code sample

new_task= client.tasks.create({'projects':'Project_id','resource_subtype':'milestone','name': whid + ' Initial Launch Communication','assignee':assignee + '@amazon.com','due_on':datetime.strftime(date_0, "%Y-%m-%d")})
client.attachments.create_attachment_for_task(new_task['gid'],file_content='data', file_name = 'Pre-Visit.msg')
client.tasks.add_subtask(new_task['gid'] ,{'name':'Pre-Visit Email Sent'})
client.tasks.add_subtask(new_task['gid'] ,{'name':'Primary KNET: Open'})
client.tasks.add_subtask(new_task['gid'] ,{'name':'Asana Access Link'})