Make rosidl packages use FindPython3 instead of FindPythonInterp

[sloretz]

This makes some rosidl packages use FindPython3 instead of FindPythonInterp.

Marking as Draft because I'm not sure if the removal of FindPythonInterp in rosidl_adapter was dependend upon by any
downstream packages - I'll make it not a draft if CI is green.

Related to ros2/python_cmake_module#6

[sloretz]

CI (build: --packages-above-and-dependencies rosidl_adapter rosidl_generator_c rosidl_generator_cpp rosidl_typesupport_introspection_c rosidl_typesupport_introspection_cpp test: --packages-select rosidl_adapter rosidl_generator_c rosidl_generator_cpp rosidl_typesupport_introspection_c rosidl_typesupport_introspection_cpp sensor_msgs)

• Linux
• Linux-aarch64
• macOS
• Windows

[nuclearsandwich]

The Rpr job will fail until ament/ament_cmake#352 is released.

[pablogs9]

Hi @sloretz and @clalancette, this PR has broken the micro-ROS build tools for micro-ROS Rolling, just the previous one works but this makes building (or generating) interfaces fail with weird behavior:

/__w/micro_ros_setup/micro_ros_setup/firmware/mcu_ws/install/lib/rosidl_typesupport_microxrcedds_c/rosidl_typesupport_microxrcedds_c: 17: import: not found
/__w/micro_ros_setup/micro_ros_setup/firmware/mcu_ws/install/lib/rosidl_typesupport_microxrcedds_c/rosidl_typesupport_microxrcedds_c: 18: import: not found
/__w/micro_ros_setup/micro_ros_setup/firmware/mcu_ws/install/lib/rosidl_typesupport_microxrcedds_c/rosidl_typesupport_microxrcedds_c: 19: import: not found
/__w/micro_ros_setup/micro_ros_setup/firmware/mcu_ws/install/lib/rosidl_typesupport_microxrcedds_c/rosidl_typesupport_microxrcedds_c: 21: from: not found
/__w/micro_ros_setup/micro_ros_setup/firmware/mcu_ws/install/lib/rosidl_typesupport_microxrcedds_c/rosidl_typesupport_microxrcedds_c: 23: Syntax error: "(" unexpected
make[2]: *** [CMakeFiles/builtin_interfaces__rosidl_typesupport_microxrcedds_c.dir/build.make:86: rosidl_typesupport_microxrcedds_c/builtin_interfaces/msg/detail/microxrcedds/duration__type_support_c.c] Error 2
make[1]: *** [CMakeFiles/Makefile2:150: CMakeFiles/builtin_interfaces__rosidl_typesupport_microxrcedds_c.dir/all] Error 2

As far as I have understood, this means that the rosidl_typesupport_microxrcedds_c is being executed as Bash script and that's why those syntax errors appear and the import command is not installed.

Later, I have found that the interpreter line is not in the first line of my file but in line 15, moving it to line 1 seems to solve the problem.

But my point now is, why using "${PYTHON_EXECUTABLE}" this file is treated as a Python script regardless of this first interpreter line (#!/usr/bin/env python3) and with the new ${python_interpreter} it behaves differently?

[clalancette]

In short, this is a bug either in this PR or one of the related ones. We are looking into it.

[mjcarroll]

It looks like this will need to be reverted: #615

[sloretz]

Hi @pablogs9 I opened micro-ROS/rosidl_typesupport_microxrcedds#34 to make those packages in micro-ROS use the FindPython3 CMake module. That PR can be merged regardless of whether this one is reverted or not.