Building example library of ROS 2

I am trying to build the example repository of ROS 2 Humble according to the tutorial. But the command colcon build --symlink-install gives the following error for all python packages. I am on Ubuntu 22.04.

What could be the reason for that?

Failed   <<< examples_rclpy_pointcloud_publisher [0.86s, exited with code 1]
    --- stderr: launch_testing_examples
    Traceback (most recent call last):
      File "/usr/lib/python3/dist-packages/colcon_core/executor/__init__.py", line 91, in __call__
        rc = await self.task(*args, **kwargs)
      File "/usr/lib/python3/dist-packages/colcon_core/task/__init__.py", line 93, in __call__
        return await task_method(*args, **kwargs)
      File "/usr/lib/python3/dist-packages/colcon_ros/task/ament_python/build.py", line 51, in build
        setup_py_data = get_setup_data(self.context.pkg, env)
      File "/usr/lib/python3/dist-packages/colcon_core/task/python/__init__.py", line 20, in get_setup_data
        return dict(pkg.metadata[key](env))
      File "/usr/lib/python3/dist-packages/colcon_ros/package_augmentation/ros_ament_python.py", line 57, in getter
        return get_setup_information(
      File "/usr/lib/python3/dist-packages/colcon_python_setup_py/package_identification/python_setup_py.py", line 241, in get_setup_information
        _setup_information_cache[hashable_env] = _get_setup_information(
      File "/usr/lib/python3/dist-packages/colcon_python_setup_py/package_identification/python_setup_py.py", line 293, in _get_setup_information
        return ast.literal_eval(output)
      File "/usr/lib/python3.10/ast.py", line 64, in literal_eval
        node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
      File "/usr/lib/python3.10/ast.py", line 50, in parse
        return compile(source, filename, mode, flags,
      File "<unknown>", line 1
        {'package_data': {}, 'dist_files': [], 'src_root': None, 'dependency_links': [], 'setup_requires': [], 'eager_resources': None, 'entry_points': {'console_scripts': []}, 'exclude_package_data': None, 'extras_require': {}, 'include_package_data': None, 'install_requires': ['setuptools'], 'namespace_packages': None, 'packages': ['launch_testing_examples'], 'python_requires': None, 'test_loader': None, 'test_runner': None, 'test_suite': None, 'tests_require': ['pytest'], 'use_2to3': None, 'zip_safe': True, 'verbose': 1, 'dry_run': 0, 'help': 0, 'command_packages': None, 'script_name': 'setup.py', 'script_args': ['--dry-run'], 'command_options': {'develop': {'script_dir': ('setup.cfg', '$base/lib/launch_testing_examples')}, 'install': {'install_scripts': ('setup.cfg', '$base/lib/launch_testing_examples')}}, 'package_dir': {}, 'py_modules': None, 'libraries': None, 'headers': None, 'ext_package': None, 'include_dirs': None, 'extra_path': None, 'scripts': None, 'data_files': [('share/ament_index/resource_index/packages', ['resource/launch_testing_examples']), ('share/launch_testing_examples', ['package.xml'])], 'password': '', 'command_obj': {}, 'have_run': {}, 'want_user_cfg': True, 'metadata': {'name': 'launch_testing_examples', 'version': '0.15.1', 'author': None, 'author_email': None, 'maintainer': 'Aditya Pande, Shane Loretz', 'maintainer_email': 'aditya.pande@openrobotics.org, shane@openrobotics.org', 'url': None, 'license': 'Apache License 2.0', 'description': 'Examples of simple launch tests', 'long_description': None, 'keywords': None, 'platforms': None, 'classifiers': None, 'download_url': None, 'provides': None, 'requires': None, 'obsoletes': None, 'long_description_content_type': None, 'project_urls': {}, 'license_file': None, '_normalized_install_requires': {'setuptools': <Requirement('setuptools')>}, '_normalized_extras_require': {}}}
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         ^
    SyntaxError: invalid syntax
I reinstalled ROS 2 but it did not resolve the problem. What else could I try?