Uw opmerkingen

Make sure that you have *-updates repositories uncommented in APT sources.list
Fixed in Ubuntu updates: https://github.com/python-greenlet/greenlet/issues/25
Какой у вас шелл? Попробуйте bash запустить в терминале и пожмякать стрелки опять.
You will probably receive some more - this is due to missing python-devel. Pay attention to "fatal error" lines - they will point you to missing header files (probably you will also need at least libevent-devel). This is because pip compiles libraries from source.
Packages are built against standard Centos 6 Python (2.6). In your case, you might want to install Ajenti directly from PyPI then: pip install ajenti
Please note the first line - you need to install Ajenti first (includes repo info) - http://support.ajenti.org/topic/349866-installing-on-centosrhel/
Now a "use custom configuration ONLY" option is available in Location settings.
/usr/lib64/python2.6/site-packages/gevent/socket.py:795: DeprecationWarning: gevent.sslold is deprecated; use gevent.ssl instead (install ssl package from PyPI)
Проблема известная - либо обновить python-gevent, python-greenlet, либо установить самые свежие из PyPI