Google appengine Send html as an email attachment
message = mail.EmailMessage(sender="My Html <html@gmail.com>",

subject="html")

message.to = "Jim <hmtl@gmail.com>"

message.body = my_body_text

message.html = my_body_html

output = StringIO.StringIO()
output.write("xxxx")

message.attachments=[("xxxx.html", output.read())]

message.send()