use catkin_pkg to parse manifests

[dirk-thomas]

Similar to ros2/ros2cli#94.

The remaining usage of ament_package in this repo (as well as in the whole ROS 2 code base) only accesses the templates stored in that package:

ament_cmake/ament_cmake_core/cmake/package_templates/templates_2_cmake.py

Lines 21 to 25 in 257c293

	from ament_package.templates import get_environment_hook_template_path
	from ament_package.templates import get_package_level_template_names
	from ament_package.templates import get_package_level_template_path
	from ament_package.templates import get_prefix_level_template_names
	from ament_package.templates import get_prefix_level_template_path

In a follow up ticket this can either handled either way:

• the templates could be moved into ament_cmake_core
• everything beside the templates could be removed from ament_package (at which point the name should maybe be reconsidered).

[mikaelarguedas]

lgtm,
If we move the templates we will be able to not release ament_package at all in Bouncy.
If we keep them here, I agree that renaming could be valuable

[dirk-thomas]

I will go ahead and merge this patch.

Any comment about the proposed follow up of ament_package would be appreciated.

[ghost]

This merge just broke my ros2 installation script (based on https://github.com/ros2/ros2/wiki/Linux-Development-Setup).

Should I now be installing catkin_pkg as a dependency before building ros2?

[dirk-thomas]

@johnmarkwayve Yes, you will need python3-catkin-pkg-modules (from Debian) or catkin_pkg (from PIP). I updated the instructions: Linux, macOS, Windows.

[ghost]

@dirk-thomas Thanks, worked perfectly