successful_request.py

import logging 
import requests

logger = logging.getLogger(__name__)
formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
fileHandle = logging.FileHandler('failed_requests.log')
fileHandle.setLevel(logging.WARNING)
fileHandle.setFormatter(formatter)
logger.addHandler(fileHandle)

# Credit to Spartas for this solution https://github.com/spartas
def successful_request(response):
  status_prefix = response.status_code // 100
  if status_prefix == 1:
    logger.debug(status_formatter(response.status_code, reponse.url))
  if status_prefix == 3:
    logger.notice(status_formatter(response.status_code, reponse.url))
  if status_prefix == 4:
    logger.warning(status_formatter(response.status_code, reponse.url))
  if status_prefix == 5:
    logger.error(status_formatter(response.status_code, reponse.url))

  return (status_prefix <= 3)

def status_formatter(code, url):
  return f'Response Code: {code} URL: {url}'

if response.status_code % 200 < 100: and the like are definitely NOT what you want to be doing here.
In your implementation, (HTTP 304 Not Modified) % 200 is 104 and would result in a false-positive error.
(HTTP 400 Bad Request) % 200 is zero and would result in false-negative error.

Here is a better implementation:

def successful_request(response):
  status_prefix = response.status_code // 100
  if status_prefix == 1:
    logger.debug(status_formatter(response.status_code, reponse.url))
  if status_prefix == 3:
    logger.notice(status_formatter(response.status_code, reponse.url))
  if status_prefix == 4:
    logger.warning(status_formatter(response.status_code, reponse.url))
  if status_prefix == 5:
    logger.error(status_formatter(response.status_code, reponse.url))

  return (status_prefix <= 3)

@spartas that is a good call. This is why I shouldn't write code past midnight. I'll update and throw an edit on my post.