Comment 9 for bug 1729754

1.3.3 (2018-07-20)
==================

- Drop support for Python < 2.6.
- Add tox testing support.
- Implement a subset of MIME multipart/form-data encoding locally rather
  than using the standard library's email module, which doesn't have good
  handling of binary parts and corrupts bytes in them that look like line
  endings in various ways depending on the Python version. [bug=1729754]