Thanks, the post is very helpful and in time.
For anyone run ubuntu 18.04 on AWS. Here is what works in Feb. 12
sudo apt update
sudo apt install python3-dev python3-pip python3-venv
python3 -m venv --system-site-packages ./venv-rasa
source ./venv-rasa/bin/activate
pip3 install -U pip
pip3 install rasa
pip3 uninstall gym
pip3 install gym==0.15.4
pip3 uninstall sanic-plugins-framework
pip3 install sanic-plugins-framework==0.8.2