Set up a virtualenv:
% curl -kLso /tmp/get-pip.py https://bootstrap.pypa.io/get-pip.py
% sudo python /tmp/get-pip.py
These commands install pip into the global site-packages directory.
% sudo pip install virtualenv
and ditto for virtualenv:
% mkdir -p ~/.virtualenvs
I like my virtualenvs under one tree in my home directory called .virtualenvs
% virtualenv ~/.virtualenvs/lxmltest
Creates a virtualenv.
% . ~/.virtualenvs/lxmltest/bin/activate
Removes the need to specify the full path to pip/python in this virtualenv.
% pip install lxml
Alternatively execute ~/.virtualenvs/lxmltest/bin/pip install lxml if you chose not to follow the previous step. Note, I'm not sure how far along you are, so some of these steps can be safely skipped. Of course, if you mess something up, you can always rm -Rf ~/.virtualenvs/lxmltest and start again from a new virtualenv.