Installing mitmproxy with pip in a python 2.7.8 virtualenv fails because the cryptography package fails to install.

The workaround is found here: http://chriskief.com/2014/03/25/installing-cryptography-via-pip-with-macports-or-homebrew/

I have openssl installed with mac ports. By first installing cryptography using the command "env ARCHFLAGS="-arch x86_64" LDFLAGS="-L/opt/local/lib" CFLAGS="-I/opt/local/include" pip install cryptography" I was able to subsequently and successfully install mitmproxy.