Deletes the currently selected custom color scheme.

def delete_scheme(self):
        """Deletes the currently selected custom color scheme."""
        scheme_name = self.current_scheme

        answer = QMessageBox.warning(self, _("Warning"),
                                     _("Are you sure you want to delete "
                                       "this scheme?"),
                                     QMessageBox.Yes | QMessageBox.No)
        if answer == QMessageBox.Yes:
            # Put the combobox in Spyder by default, when deleting a scheme
            names = self.get_option('names')
            self.set_scheme('spyder')
            self.schemes_combobox.setCurrentIndex(names.index('spyder'))
            self.set_option('selected', 'spyder')

            # Delete from custom_names
            custom_names = self.get_option('custom_names', [])
            if scheme_name in custom_names:
                custom_names.remove(scheme_name)
            self.set_option('custom_names', custom_names)

            # Delete config options
            for key in syntaxhighlighters.COLOR_SCHEME_KEYS:
                option = "{0}/{1}".format(scheme_name, key)
                CONF.remove_option(self.CONF_SECTION, option)
            CONF.remove_option(self.CONF_SECTION,
                               "{0}/name".format(scheme_name))

            self.update_combobox()
            self.update_preview()