[ROS2] Failed to load entry point 'launch'

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Hi,

I wanted to start my launch file from command line with following command

ros2 launch <pkg_name> <file>

now i got this error:

Failed to load entry point 'launch': cannot import name 'get_typed_value' from 'launch.frontend.type_utils' (/home/lwnmil2/develop_ws/install/launch/lib/python3.8/site-packages/launch/frontend/type_utils.py)
Traceback (most recent call last):
  File "/opt/ros/foxy/bin/ros2", line 11, in <module>
    load_entry_point('ros2cli==0.9.7', 'console_scripts', 'ros2')()
  File "/opt/ros/foxy/lib/python3.8/site-packages/ros2cli/cli.py", line 39, in main
    add_subparsers_on_demand(
  File "/opt/ros/foxy/lib/python3.8/site-packages/ros2cli/command/__init__.py", line 236, in add_subparsers_on_demand
    extension = command_extensions[name]
KeyError: 'launch'

When I open the help of the ros2 command the same error message is shown and there is no entry for the ros2 command:

ros2 -h


    Failed to load entry point 'launch': cannot import name 'get_typed_value' from 'launch.frontend.type_utils' (/home/lwnmil2/develop_ws/install/launch/lib/python3.8/site-packages/launch/frontend/type_utils.py)
usage: ros2 [-h] Call `ros2 <command> -h` for more detailed usage. ...

ros2 is an extensible command-line tool for ROS 2.

optional arguments:
  -h, --help            show this help message and exit

Commands:
  action     Various action related sub-commands
  bag        Various rosbag related sub-commands
  component  Various component related sub-commands
  daemon     Various daemon related sub-commands
  doctor     Check ROS setup and other potential issues
  interface  Show information about ROS interfaces
  lifecycle  Various lifecycle related sub-commands
  multicast  Various multicast related sub-commands
  node       Various node related sub-commands
  param      Various param related sub-commands
  pkg        Various package related sub-commands
  run        Run a package specific executable
  security   Various security related sub-commands
  service    Various service related sub-commands
  topic      Various topic related sub-commands
  wtf        Use `wtf` as alias to `doctor`

  Call `ros2 <command> -h` for more detailed usage.

What is broken on my system? and how can i fix it? I use Ubuntu 20.04 with foxy