LetsEncrypt, CentOS 7 Stacktrace, 2015 Nov 20

$ sudo ./letsencrypt-auto certonly -a standalone -d justinwflory.com --agree-dev-preview --server https://acme-v01.api.letsencrypt.org/directory
Updating letsencrypt and virtual environment dependencies..../root/.local/share/letsencrypt/lib/python2.7/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  InsecurePlatformWarning
.Requirement already satisfied (use --upgrade to upgrade): ConfigArgParse from git+https://github.com/kuba/[email protected]#egg=ConfigArgParse in /root/.local/share/letsencrypt/lib/python2.7/site-packages (from -r py26reqs.txt (line 1))
.Command "/root/.local/share/letsencrypt/bin/python2 -c "import setuptools, tokenize;__file__='/tmp/pip-build-MAVDX2/cryptography/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-DD4AGH-record/install-record.txt --single-version-externally-managed --compile --install-headers /root/.local/share/letsencrypt/include/site/python2.7/cryptography" failed with error code 1 in /tmp/pip-build-MAVDX2/cryptography