Fix “openssl/aes.h file not found” on OS X

I got an issue when installing pusher-http-python, python library for https://pusher.com/ on OS X.
My problem solved just run this single line in terminal.

env LDFLAGS="-L$(brew --prefix openssl)/lib" CFLAGS="-I$(brew --prefix openssl)/include" pip install cryptography

Reference:
https://github.com/pyca/cryptography/issues/2350
http://masnun.com/2015/12/01/fixing-fatal-error-opensslaes-h-file-not-found-on-os-x.html