No need for a separate /usr/sbin/sendmail delivery component, just use direct:

Refs #15.
Use subprocess for /usr/sbin/sendmail invocation:

os.popen is quasi-deprecated, also do cleaner argument handling that
doesn't depend on shell parsing and makes the command templating simpler.
Don't invoke /usr/sbin/sendmail when running tests!  Also add actual asserts.

Refs #15.
pep8
Oops, fix a coverage hole I introduced in a typo in some pep8 fixes
Fix some coverage holes in the /usr/sbin/sendmail tests:

Closes #15
Fix some coverage holes
Fix deprecated assert methods
Add test case for quoted-printable encoding of multipart/alternative:

refs Pylons/pyramid_mailer#29