Validate the output of an :class:`APISpec` object against the
    OpenAPI specification.

    Note: Requires installing apispec with the ``[validation]`` extras.
    ::

        pip install 'apispec[validation]'

    :raise: apispec.exceptions.OpenAPIError if validation fails.

def validate_spec(spec):
    """Validate the output of an :class:`APISpec` object against the
    OpenAPI specification.

    Note: Requires installing apispec with the ``[validation]`` extras.
    ::

        pip install 'apispec[validation]'

    :raise: apispec.exceptions.OpenAPIError if validation fails.
    """
    try:
        import prance
    except ImportError as error:  # re-raise with a more verbose message
        exc_class = type(error)
        raise exc_class(
            "validate_spec requires prance to be installed. "
            "You can install all validation requirements using:\n"
            "    pip install 'apispec[validation]'"
        )
    parser_kwargs = {}
    if spec.openapi_version.version[0] == 3:
        parser_kwargs["backend"] = "openapi-spec-validator"
    try:
        prance.BaseParser(spec_string=json.dumps(spec.to_dict()), **parser_kwargs)
    except prance.ValidationError as err:
        raise exceptions.OpenAPIError(*err.args)
    else:
        return True