Installing Cryptography via Pip with MacPorts or Homebrew

If you have tried installing / updating pyOpenSSL to version 0.14 you may have run into an issue when it tries to install the required package cryptography. The specific error I encountered was:

To get around this, you’ll need to set some environment variables before installing cryptography:

A pull request has been opened to add this to the documentation but as of this writing it has not yet been merged.