I answered on the duplicate thread you opened 2.5 hours later. To repeat:
there's a bug in your code, a missing `from email import encoders` at the
top. BTW, I think your bug has nothing to do with Google App Engine.
Alex
On Fri, Mar 3, 2017 at 7:08 AM, Guillaume France
I'm struggling with the create_message_with_attachment (the rest works,
create_message_without_attachment works ).
I did read google documentation. The stack thread talking about it focus on
complicate point (while mixing up the different python version). Posting
this in stack will be