How to use the cssselect.SelectorError function in cssselect

except splunk.ResourceNotFound:
                cherrypy.response.status = 202
                return self.render_error_json(_("Proxy server information could not be obtained"))

            # Scrape the page
            result = web_scraper.scrape_page(url, selector, **kw)

        except FieldValidationException as e:
            cherrypy.response.status = 220
            return self.render_error_json(_(str(e)))

        except ServerNotFoundError as e:
            cherrypy.response.status = 220
            return self.render_error_json(_(str(e)))

        except (SelectorError, SelectorSyntaxError, ExpressionError):
            cherrypy.response.status = 220
            return self.render_error_json(_("Selector is invalid. "))

        except LoginFormNotFound:
            cherrypy.response.status = 220
            return self.render_error_json("Login form was not found")

        except FormAuthenticationFailed:
            cherrypy.response.status = 220
            return self.render_error_json("Form authentication failed")

        except Exception as e:
            cherrypy.response.status = 500

            logger.exception("Error generated during execution")
            return self.render_error_json(_(str(e)))

web_scraper.set_proxy(proxy_type, proxy_server, proxy_port, proxy_user, proxy_password)

            except ResourceNotFound:
                return self.render_error_json("Proxy server information could not be obtained", 202)

            # Scrape the page
            result = web_scraper.scrape_page(url, selector, **kw)

        except FieldValidationException as e:
            return self.render_error_json(str(e), 220)

        except ServerNotFoundError as e:
            return self.render_error_json(str(e), 220)

        except (SelectorError, SelectorSyntaxError, ExpressionError):
            return self.render_error_json("Selector is invalid. ", 220)

        except LoginFormNotFound:
            return self.render_error_json("Login form was not found", 220)

        except FormAuthenticationFailed:
            return self.render_error_json("Form authentication failed", 220)

        except Exception as e:
            logger.exception("Error generated during execution")
            return self.render_error_json(str(e), 500)

        # Return the information
        if 'include_first_result_only' in kwargs:
            return self.render_json(result[0])
        else:

"""

from __future__ import absolute_import

from . import etree
try:
    import cssselect as external_cssselect
except ImportError:
    raise ImportError(
        'cssselect does not seem to be installed. '
        'See http://packages.python.org/cssselect/')


SelectorSyntaxError = external_cssselect.SelectorSyntaxError
ExpressionError = external_cssselect.ExpressionError
SelectorError = external_cssselect.SelectorError


__all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
           'CSSSelector']


class LxmlTranslator(external_cssselect.GenericTranslator):
    """
    A custom CSS selector to XPath translator with lxml-specific extensions.
    """
    def xpath_contains_function(self, xpath, function):
        # Defined there, removed in later drafts:
        # http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
        if function.argument_types() not in (['STRING'], ['IDENT']):
            raise ExpressionError(
                "Expected a single string or ident for :contains(), got %r"

"""

from __future__ import absolute_import

from . import etree
try:
    import cssselect as external_cssselect
except ImportError:
    raise ImportError(
        'cssselect does not seem to be installed. '
        'See http://packages.python.org/cssselect/')


SelectorSyntaxError = external_cssselect.SelectorSyntaxError
ExpressionError = external_cssselect.ExpressionError
SelectorError = external_cssselect.SelectorError


__all__ = ['SelectorSyntaxError', 'ExpressionError', 'SelectorError',
           'CSSSelector']


class LxmlTranslator(external_cssselect.GenericTranslator):
    """
    A custom CSS selector to XPath translator with lxml-specific extensions.
    """
    def xpath_contains_function(self, xpath, function):
        # Defined there, removed in later drafts:
        # http://www.w3.org/TR/2001/CR-css3-selectors-20011113/#content-selectors
        if function.argument_types() not in (['STRING'], ['IDENT']):
            raise ExpressionError(
                "Expected a single string or ident for :contains(), got %r"