How to use the ltk.exceptions.RequestFailedError function in ltk

try:
        if json:
            error = json['messages'][0]
        file_name = file_name.replace("Status of ", "")
        if file_name is not None and doc_id is not None:
            error = error.replace(doc_id, file_name+" ("+doc_id+")")
        # Sometimes api returns vague errors like 'Unknown error'
        if error == 'Unknown error':
            error = error_message
        if not is_warning:
            raise exceptions.RequestFailedError(error)
        # warnings.warn(error)
        logger.error(error)
    except (AttributeError, IndexError):
        if not is_warning:
            raise exceptions.RequestFailedError(error_message)
        # warnings.warn(error_message)
        logger.error(error_message)

def raise_error(json, error_message, is_warning=False, doc_id=None, file_name=None):
    try:
        error = ""
        if json:
            error = json['messages'][0]
        if file_name:
            file_name = file_name.replace("Status of ", "")
        if file_name is not None and doc_id is not None:
            error = error.replace(doc_id, file_name+" ("+doc_id+")")
        # Sometimes api returns vague errors like 'Unknown error'
        if error == 'Unknown error':
            error = error_message
        if not is_warning:
            raise exceptions.RequestFailedError(error)
        # warnings.warn(error)
        if error:
            error = error+"\n"
        logger.error(error+error_message)
    except (AttributeError, IndexError):
        if not is_warning:
            raise exceptions.RequestFailedError(error_message)
        # warnings.warn(error_message)
        logger.error(error_message)

def get_project_info(self, community_id):
        response = self.list_projects(community_id)
        info = {}
        if response.status_code == 200:
            if int(response.json()['properties']['total']) == 0:
                return info
            entities = response.json()['entities']
            for entity in entities:
                info[entity['properties']['id']] = entity['properties']['title']
            return info
        elif response.status_code == 204:
            return info
        else:
            raise RequestFailedError("Unable to get existing projects")

def import_locale_info(self, document_id, poll=False):
        locale_progress = {}
        response = self.api.document_translation_status(document_id)
        if response.status_code != 200:
            if poll:
                return {}
            else:
                # raise_error(response.json(), 'Failed to get locale details of document', True)
                raise exceptions.RequestFailedError('Failed to get locale details of document')
        try:
            for entry in response.json()['entities']:
                curr_locale = entry['properties']['locale_code']
                curr_progress = int(entry['properties']['percent_complete'])
                curr_locale = curr_locale.replace('-', '_')
                locale_progress[curr_locale] = curr_progress
        except KeyError:
            pass
        return locale_progress

def import_locale_info(self, document_id, poll=False):
        locale_progress = {}
        response = self.api.document_translation_status(document_id)
        if response.status_code != 200:
            if poll:
                return {}
            else:
                # raise_error(response.json(), 'Failed to get locale details of document', True)
                raise exceptions.RequestFailedError('Failed to get locale details of document')
        try:
            for entry in response.json()['entities']:
                curr_locale = entry['properties']['locale_code']
                curr_progress = int(entry['properties']['percent_complete'])
                curr_locale = curr_locale.replace('-', '_')
                locale_progress[curr_locale] = curr_progress
        except KeyError:
            pass
        return locale_progress

def import_locale_info(self, document_id, poll=False, include_cancelled=False):
        locale_progress = {}
        response = self.api.document_translation_status(document_id)
        if response.status_code != 200:
            if poll or response.status_code == 404:
                return {}
            else:
                # raise_error(response.json(), 'Failed to get locale details of document', True)
                raise exceptions.RequestFailedError('Failed to get locale details of document')
        try:
            for entry in response.json()['entities']:
                curr_locale = entry['properties']['locale_code']
                curr_progress = int(entry['properties']['percent_complete'])
                curr_status = entry['properties']['status']
                curr_locale = curr_locale.replace('-', '_')
                if include_cancelled or (curr_status.upper() != 'CANCELLED'):
                    locale_progress[curr_locale] = curr_progress
        except KeyError:
            pass
        return locale_progress

def list_locale_action(self):
        locale_info = []
        response = self.api.list_locales()
        if response.status_code != 200:
            raise exceptions.RequestFailedError("Failed to get locale codes")
        locale_json = response.json()
        for entry in locale_json:
            locale_code = locale_json[entry]['locale']
            language = locale_json[entry]['language_name']
            country = locale_json[entry]['country_name']
            locale_info.append((locale_code, language, country))
        for locale in sorted(locale_info):
            if not len(locale[2]):  # Arabic
                print ("{0} ({1})".format(locale[0], locale[1]))
            else:
                print ("{0} ({1}, {2})".format(locale[0], locale[1], locale[2]))

def reference_remove(filename, doc_id, remove_all):
    """Deletes reference material attached to a document on Lingotek."""
    try:
        action = reference_action.ReferenceAction(os.getcwd())
        init_logger(action.path)
        action.reference_remove_action(filename, doc_id, remove_all)
    except (UninitializedError, RequestFailedError) as e:
        print_log(e)
        logger.error(e)
        return

def import_locale_info(self, document_id, poll=False):
        locale_progress = {}
        response = self.api.document_translation_status(document_id)
        if response.status_code != 200:
            if poll or response.status_code == 404:
                return {}
            else:
                # raise_error(response.json(), 'Failed to get locale details of document', True)
                raise exceptions.RequestFailedError('Failed to get locale details of document')
        try:
            for entry in response.json()['entities']:
                curr_locale = entry['properties']['locale_code']
                curr_progress = int(entry['properties']['percent_complete'])
                curr_locale = curr_locale.replace('-', '_')
                locale_progress[curr_locale] = curr_progress
        except KeyError:
            pass
        return locale_progress