Spawn robot ROS2: spawn_robot.py now found on the libexec directory

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I'm running ros2 Foxy in Ubuntu 20.04. I'm trying to spawn a robot, generated from a XACRO file into an empty world in gazebo. I've been launching gazebo with

ros2 launch gazebo_ros gazebo.launch.py

Then spawning my robot with

ros2 launch do_description spawn_robot.launch.py

But I keep getting the error

"executable 'spawn_robot.py' not found on the libexec directory '/home/samking7185/dev_ws/install/do_description/lib/do_description' "

Even though the spawn_robot.py shows up in the libexec directory. Do I need to do something else to convert this spawn_robot.py file to an actual executable?

I've create a python script to spawn a robot here, spawn_robot.py:

#!/usr/bin/python3
# -*- coding: utf-8 -*-
import os
import sys
import rclpy
from gazebo_msgs.srv import SpawnEntity

def main(args=None):
    rclpy.init(args=args)
    node = rclpy.create_node('spawn entity')
    cli = node.create_client(SpawnEntity, '/spawn_entity')

    content = sys.argv[1]

    req = SpawnEntity.Request()
    req.name = "robot"
    req.xml = content
    req.robot_namespace = ""
    req.reference_frame = "world"

    while not cli.wait_for_service(timeout_sec=1.0):
        node.get_logger().info('service not available, waiting again...')

    future = cli.call_async(req)
    rclpy.spin_until_future_complete(node, future)

    if future.result() is not None:
        node.get_logger().info(
            'Result ' + str(future.result().success) + " " + future.result().status_message)
    else:
        node.get_logger().info('Service call failed %r' % (future.exception(),))

    node.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()

I've included the call to my executable in my launch file, spawn_robot.launch.py:

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node

import xacro

def generate_launch_description():

    use_sim_time = LaunchConfiguration('use_sim_time', default='true')

    # urdf = os.path.join(get_package_share_directory('box_car_description'), 'robot/', 'box_bot.urdf')    
    # assert os.path.exists(urdf), "Thebox_bot.urdf doesnt exist in "+str(urdf)

    xacro_file = os.path.join(get_package_share_directory('do_description'), 'urdf/', 'do_robot.xacro')    
    assert os.path.exists(xacro_file), "The do_robot.xacro doesnt exist in "+str(xacro_file)
    robot_description_config = xacro.process_file(xacro_file)

    robot_desc = robot_description_config.toxml()

    return LaunchDescription([
        DeclareLaunchArgument(
            'use_sim_time',
            default_value='false',
            description='Use simulation (Gazebo) clock if true'),
        Node(package='do_description', executable='spawn_robot.py', arguments=[robot_desc], output='screen'),
        Node(
            package="robot_state_publisher",
            executable="robot_state_publisher",
            name="robot_state_publisher",
            parameters=[
                {"robot_description": robot_desc}],
            output="screen"),
    ])

And populated the PROGRAMS field in my CMAKE file:

cmake_minimum_required(VERSION 3.5)
project(do_description)

# Default to C99
if(NOT CMAKE_C_STANDARD)
  set(CMAKE_C_STANDARD 99)
endif()

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(ament_cmake REQUIRED)
find_package(urdf REQUIRED)
find_package(xacro REQUIRED)


if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  ament_lint_auto_find_test_dependencies()
endif()

install(
  DIRECTORY
    launch
    urdf
  DESTINATION
    share/${PROJECT_NAME}/
)

install(
  PROGRAMS
    launch/spawn_robot.py
  DESTINATION lib/${PROJECT_NAME}
)

ament_package()