E ROS2 Foxy on 18.04

Solve signatures invalid F42ED6FBAB17C654

This command helps:

curl http://repo.ros2.org/repos.key | sudo apt-key add -

python3-rosdep

python3-rosdep-modules complains about unmet dependencies from python3-catkin-pkg, python3-rosdistro, and python3-rospkg but installing them via

sudo apt install python3-catkin-pkg python3-rosdistro python3-rospkg

then

apt install python3-rosdep-modules

and finally

sudo apt install python3-rosdistro

Follow the official Building ROS 2 on Ubuntu commands

docs.ros.org/en/foxy/Installation/Ubuntu-Development-Setup.html