input: Write a python function to check if a URL is accessible and return 'Success!' if the status code is 200, otherwise return 'An error has occurred.'
  assert check_url_access('https://www.example.com/') == 'Success!'
  assert check_url_access('https://www.nonexistentwebsite.com/') == 'An error has occurred.'
  assert check_url_access('https://www.google.com/') == 'Success!'
output: import requests
  
  def check_url_access(url):
      try:
          response = requests.get(url)
          if response.status_code == 200:
              return 'Success!'
          else:
              return 'An error has occurred.'
      except requests.RequestException:
          return 'An error has occurred.'