old_contents: import random
  import string
  
  
  def rand_str(n=8):
      """Return a random string of length n"""
      return ''.join(random.SystemRandom().choice(string.letters)
                     for _ in range(n))
  
  def rand_email():
      return 'test.email.{}@userkit.co'.format(rand_str())
  
new_contents: import random
  import string
  
  
  def rand_str(n=8):
      """Return a random string of length n"""
      return ''.join(random.SystemRandom().choice(string.ascii_lowercase)
                     for _ in range(n))
  
  
  def rand_email():
      return 'test.email.{}@userkit.co'.format(rand_str())
  
subject: Fix Python3 bug in tests/util.py