This patches a bug in Twisted Web’s Agent, where BrowserLikePolicyForHTTPS would not honour the trust root given, and would use the system trust root instead. This would have broken, for example, attempting to pin the issuer for your HTTPS application because you only trust one issuer.
Note: on OS X, with the system OpenSSL, you still can't fully rely on this API for issuer pinning, due to modifications by Apple — please see https://hynek.me/articles/apple-openssl-verification-surprises/ for more details.
You can find the downloads at https://pypi.python.org/pypi/Twisted (or alternatively http://twistedmatrix.com/trac/wiki/Downloads). The NEWS file is also available at https://twistedmatrix.com/trac/browser/tags/releases/twisted-14.0.1/NEWS?format=raw.
Thanks for Alex Gaynor for discovering the bug, Glyph & Alex for developing a patch, and David Reid for reviewing it.
14.0.2 is a bugfix patch for distributors, that corrects a failing test in the patch for 14.0.1.
Edit, 22nd Sep 2014: CVE-2014-7143 has been assigned for this issue.