pydantic >2.9 causes failures with launch file

[anfederman]

ros2 launch usb_cam camera.launch.py
[INFO] [launch]: All log files can be found below /home/ubiqlap/.ros/log/2024-11-16-08-31-53-762719-ubiqlap-X540LA-5691
[INFO] [launch]: Default logging verbosity is set to INFO
[ERROR] [launch]: Caught exception in launch (see debug for traceback): Caught multiple exceptions when trying to load file of format [py]:

• PydanticUserError: If you use @root_validator with pre=False (the default) you MUST specify skip_on_failure=True. Note that @root_validator is deprecated and should be replaced with @model_validator.

For further information visit https://errors.pydantic.dev/2.9/u/root-validator-pre-skip

• InvalidFrontendLaunchFileError: The launch file may have a syntax error, or its format is unknown

[flynneva]

@anfederman thanks for reporting the error! Looks like we need to update the launch file to the latest pydantic syntax.

I won't have time to tackle this anytime soon unfortunately, but would happily review a PR

[flynneva]

@anfederman so I believe this is only an issue if you use pydantic>=2.9 it looks like.

For Humble - using rosdep to install pydantic would be like calling sudo apt-get install python3-pydantic....which isnt > 2.9.

Even for Rolling on Ubuntu 24.04 (what I have locally) it will still install an older version of pydantic: https://launchpad.net/ubuntu/+source/pydantic

So not sure I want to make this fix just yet, but will probably have to make it once Rolling switches to a new Ubuntu distro.