This should work. give a shot.
pip install rasa-x -i https://pypi.rasa.com/simple --trusted-host pypi.python.org --trusted-host files.pythonhosted.org --trusted-host pypi.org --trusted-host pypi.rasa.com --trusted-host storage.googleapis.com --proxy=proxy.example.com
(Installation issue with rasa-x on office laptop - #4 by HarishMunagapati)`