patchbomb: use email.mime.multipart instead of email.MIMEMultipart...
patchbomb: use email.mime.multipart instead of email.MIMEMultipart
The later was removed in Python 3.
On python 2:
>>> email.MIMEMultipart.MIMEMultipart is email.mime.multipart.MIMEMultipart
True
Differential Revision:
https://phab.mercurial-scm.org/D3835
