ImportError when building ROS2 Bouncy Bolson on Ubuntu 16.04 from source

edit

It looks like you are using an outdated version of the code. There are no package in Bouncy that still uses ament_package to parse package.xml files. Now the package parsing is done using catkin_pkg. As a consequence the parse_package_string function has been removed from ament_package

Can you make sure to download the Bouncy version of the code for all repositories?

I recommend doing it in an empty workspace to make sure you don't have any legacy Ardent repositories in your workspace.

You can do so by running:

mkdir -p bouncy_ws/src
wget https://raw.githubusercontent.com/ros2/ros2/release-latest/ros2.repos
vcs import src < ros2.repos