Ros2 launch gives an error in ros2_control_demos

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Hello

I am trying ros2_contro_demos.

Follow the tutorial,

git clone -b galactic https://github.com/ros-controls/ros2_control
git clone -b galactic https://github.com/ros-controls/ros2_controllers
git clone -b galactic https://github.com/ros-controls/ros2_control_demos

and

 rosdep install --from-paths src --ignore-src -r -y
 colcon build --symlink-install

I have finished to build with some additional packages.

But, I hit

ros2 launch rrbot_description view_robot.launch.py

I get an error below

raise SubstitutionFailure("executable '{}' not found on the PATH".format(self.name))
launch.substitutions.substitution_failure.SubstitutionFailure: executable '[<launch.substitutions.text_substitution.TextSubstitution object at 0x7f72314f7eb0>]' not found on the PATH

I have no idea what error this is.

Please help me.

thanks.

My setup is below.

Ubuntu20.04 ros2:galactic