if error easy_install -U gevent==1.1b3 the apt-get install gcc

To fix problem, execute the commands below.

1. Install python tools and dev
   $ install python-setuptools python-dev
2. Install gevent, in version 1.1b3
   $ easy_install -U gevent==1.1b3
3. Downgrade ssl version of protocol
   $ sed -i -e s/ssl_version=PROTOCOL_SSLv3/ssl_version=PROTOCOL_SSLv23/ /usr/local/lib/python2.7/dist-packages/gevent-1.1b3-py2.7-linux-x86_64.egg/gevent/ssl.py
4. Restart ajenti
   $ service ajenti restart

https://github.com/ajenti/ajenti/issues/702