How to use the confuse.exceptions.ConfigError function in confuse

"""Get the path to the user configuration directory. The
        directory is guaranteed to exist as a postcondition (one may be
        created if none exist).

        If the application's ``...DIR`` environment variable is set, it
        is used as the configuration directory. Otherwise,
        platform-specific standard configuration locations are searched
        for a ``config.yaml`` file. If no configuration file is found, a
        fallback path is used.
        """
        # If environment variable is set, use it.
        if self._env_var in os.environ:
            appdir = os.environ[self._env_var]
            appdir = os.path.abspath(os.path.expanduser(appdir))
            if os.path.isfile(appdir):
                raise ConfigError(u'{0} must be a directory'.format(
                    self._env_var
                ))

        else:
            # Search platform-specific locations. If no config file is
            # found, fall back to the first directory in the list.
            configdirs = util.config_dirs()
            for confdir in configdirs:
                appdir = os.path.join(confdir, self.appname)
                if os.path.isfile(os.path.join(appdir, CONFIG_FILENAME)):
                    break
            else:
                appdir = os.path.join(configdirs[0], self.appname)

        # Ensure that the directory exists.
        if not os.path.isdir(appdir):

view,
                            self.template
                        )

                        next_template.subtemplates[view.key] = as_template(
                            candidate
                        )
                    else:
                        next_template = MappingTemplate({view.key: candidate})

                    return view.parent.get(next_template)[view.key]
                else:
                    return view.get(candidate)
            except exceptions.ConfigTemplateError:
                raise
            except exceptions.ConfigError:
                pass
            except ValueError as exc:
                raise exceptions.ConfigTemplateError(exc)

        self.fail(
            u'must be one of {0}, not {1}'.format(
                repr(self.allowed), repr(value)
            ),
            view
        )

YAML_TAB_PROBLEM = "found character '\\t' that cannot start any token"

# Exceptions.


class ConfigError(Exception):
    """Base class for exceptions raised when querying a configuration.
    """


class NotFoundError(ConfigError):
    """A requested value could not be found in the configuration trees.
    """


class ConfigValueError(ConfigError):
    """The value in the configuration is illegal."""


class ConfigTypeError(ConfigValueError):
    """The value in the configuration did not match the expected type.
    """


class ConfigTemplateError(ConfigError):
    """Base class for exceptions raised because of an invalid template.
    """


class ConfigReadError(ConfigError):
    """A configuration file could not be read."""
    def __init__(self, filename, reason=None):

class ConfigValueError(ConfigError):
    """The value in the configuration is illegal."""


class ConfigTypeError(ConfigValueError):
    """The value in the configuration did not match the expected type.
    """


class ConfigTemplateError(ConfigError):
    """Base class for exceptions raised because of an invalid template.
    """


class ConfigReadError(ConfigError):
    """A configuration file could not be read."""
    def __init__(self, filename, reason=None):
        self.filename = filename
        self.reason = reason

        message = u'file {0} could not be read'.format(filename)
        if (isinstance(reason, yaml.scanner.ScannerError)
                and reason.problem == YAML_TAB_PROBLEM):
            # Special-case error message for tab indentation in YAML markup.
            message += u': found tab character at line {0}, column {1}'.format(
                reason.problem_mark.line + 1,
                reason.problem_mark.column + 1,
            )
        elif reason:
            # Generic error message uses exception's message.
            message += u': {0}'.format(reason)

__all__ = [
    'ConfigError', 'NotFoundError', 'ConfigValueError', 'ConfigTypeError',
    'ConfigTemplateError', 'ConfigReadError']

YAML_TAB_PROBLEM = "found character '\\t' that cannot start any token"

# Exceptions.


class ConfigError(Exception):
    """Base class for exceptions raised when querying a configuration.
    """


class NotFoundError(ConfigError):
    """A requested value could not be found in the configuration trees.
    """


class ConfigValueError(ConfigError):
    """The value in the configuration is illegal."""


class ConfigTypeError(ConfigValueError):
    """The value in the configuration did not match the expected type.
    """


class ConfigTemplateError(ConfigError):
    """Base class for exceptions raised because of an invalid template.
    """

class NotFoundError(ConfigError):
    """A requested value could not be found in the configuration trees.
    """


class ConfigValueError(ConfigError):
    """The value in the configuration is illegal."""


class ConfigTypeError(ConfigValueError):
    """The value in the configuration did not match the expected type.
    """


class ConfigTemplateError(ConfigError):
    """Base class for exceptions raised because of an invalid template.
    """


class ConfigReadError(ConfigError):
    """A configuration file could not be read."""
    def __init__(self, filename, reason=None):
        self.filename = filename
        self.reason = reason

        message = u'file {0} could not be read'.format(filename)
        if (isinstance(reason, yaml.scanner.ScannerError)
                and reason.problem == YAML_TAB_PROBLEM):
            # Special-case error message for tab indentation in YAML markup.
            message += u': found tab character at line {0}, column {1}'.format(
                reason.problem_mark.line + 1,