errors installing cryptography_one solution

openSSL_solution.txt

brew install openssl

then brew gives a hint:

Apple has deprecated use of OpenSSL in favor of its own TLS and crypto libraries

Generally there are no consequences of this for you. If you build your
own software and it requires this formula, you'll need to add to your
build variables:

    LDFLAGS:  -L/usr/local/opt/openssl/lib
    CPPFLAGS: -I/usr/local/opt/openssl/include
    PKG_CONFIG_PATH: /usr/local/opt/openssl/lib/pkgconfig

So just export these env vars and rerun your favorite pip install (or better to avoid havoc in future add following to your ~/.bash_profile:

export LDFLAGS="-L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/openssl/include"
export PKG_CONFIG_PATH="/usr/local/opt/openssl/lib/pkgconfig"

another solution was just to upgrade pip
pip install --upgrade pip

for reference
pyca/cryptography#2692

https://stackoverflow.com/questions/22073516/failed-to-install-python-cryptography-package-with-pip-and-setup-py

Since this SO question keeps coming up I'll drop a response here too (I am one of the pyca/cryptography developers). Here's what you need to reliably install pyca/cryptography on the 3 major platforms.

Please note in all these cases it is highly recommended that you install into a virtualenv and not into the global package space. This is not specific to cryptography but rather is generic advice to keep your Python installation reliable. The global package space in OS provided Pythons is owned by the system and installing things via pip into it is asking for trouble.

Windows

Upgrade to the latest pip (8.1.2 as of June 2016) and just pip install cryptography

cryptography and cffi are both shipped as statically linked wheels.

OS X

Upgrade to the latest pip (8.1.2 as of June 2016) and just pip install cryptography

cryptography and cffi are both shipped as statically linked wheels. This will work for pyenv Python, system Python, homebrew Python, etc. As long as you're on the latest pip you won't even need a compiler.

Linux

As of version 2.0 cryptography ships manylinux1 wheels. This means users with pip 8.1+ running on a glibc-based distribution (almost everything except Alpine Linux) and on x86/x86-64 (sorry Raspberry Pi people) no longer need a compiler or headers because you'll get a precompiled wheel automatically. So, first thing you should try is upgrading your pip!

If you aren't manylinux1 compatible then here's what you need to do:

You'll need a C compiler, libffi + its development headers, and openssl + its development headers.

Debian or Ubuntu derived distributions

apt-get install build-essential libssl-dev libffi-dev python-dev followed by

pip install cryptography

Red Hat derived distributions

yum install gcc openssl-devel libffi-devel python-devel followed by

pip install cryptography