How to use the briefcase.exceptions.BriefcaseConfigError function in briefcase

[tool.briefcase]
        version = "1.2.3"
        description = "A sample app"
        bundle = "org.beeware"
        mystery = 'default'

        [tool.briefcase.app.firstapp]
        sources = ['src/firstapp']

    """)

    # Parse the configuration.
    # Even though the global config has everything needed for the default
    # configuration, it's missing a required option for the custom class.
    with pytest.raises(
        BriefcaseConfigError,
        match=r"Global configuration is incomplete \(missing 'foo'\)"
    ):
        other_command.parse_config(filename)

def test_missing_config(base_command):
    "If the configuration file doesn't exit, raise an error"
    filename = str(base_command.base_path / 'does_not_exist.toml')
    with pytest.raises(BriefcaseConfigError, match="configuration file not found"):
        base_command.parse_config(filename)

def test_invalid_toml():
    "If the config file isn't TOML, raise an error"
    config_file = StringIO("this is not toml!")

    with pytest.raises(BriefcaseConfigError, match="Invalid pyproject.toml"):
        parse_config(config_file, platform='macos', output_format='app')

def test_no_briefcase_section():
    "If the config file doesn't contain a briefcase tool section, raise an error"
    config_file = StringIO(
        """
        [build-system]
        requires = ["briefcase"]

        [tool.section]
        name="value"
        number=42
        """
    )

    with pytest.raises(BriefcaseConfigError, match="No tool.briefcase section"):
        parse_config(config_file, platform='macos', output_format='app')

def test_valid_app_name(name):
    try:
        AppConfig(
            name=name,
            version="1.2.3",
            bundle="org.beeware",
            description="A simple app",
            sources=['src/' + name.replace('-', '_')]
        )
    except BriefcaseConfigError:
        pytest.fail('{name} should be valid'.format(name=name))

def test_no_source_for_app():
    with pytest.raises(BriefcaseConfigError, match=r" does not include a package named 'my_app'\."):
        AppConfig(
            name='my-app',
            version="1.2.3",
            bundle="org.beeware",
            description="A simple app",
            sources=['src/something', 'src/other']
        )

except TypeError:
        # Inspect the GlobalConfig constructor to find which
        # parameters are required and don't have a default
        # value.
        required_args = {
            name
            for name, param in inspect.signature(klass.__init__).parameters.items()
            if param.default == inspect._empty
            and name not in {'self', 'kwargs'}
        }
        missing_args = required_args - config.keys()
        missing = ', '.join(
            "'{arg}'".format(arg=arg)
            for arg in sorted(missing_args)
        )
        raise BriefcaseConfigError(
            "{msg} is incomplete (missing {missing})".format(
                msg=msg,
                missing=missing
            )

msg="Global configuration"
                )

                for app_name, app_config in app_configs.items():
                    # Construct an AppConfig object with the final set of
                    # configuration options for the app.
                    self.apps[app_name] = create_config(
                        klass=self.APP_CONFIG_CLASS,
                        config=app_config,
                        msg="Configuration for '{app_name}'".format(
                            app_name=app_name
                        )
                    )

        except FileNotFoundError:
            raise BriefcaseConfigError('configuration file not found')