old_contents: import re
  import pexpect
  
  def auth(username, password):
      clean_username = re.sub('[^a-zA-Z0-9]', '_', username)
      cmd = [ 'su', '--login', '-c /bin/true', clean_username ]
  
      p = pexpect.spawn(' '.join(cmd), timeout=60)
      p.expect('.*assword.*')
      p.sendline(password)
      p.expect(pexpect.EOF)
      p.close()
  
      return p.exitstatus == 0    
      
  
new_contents: import re
  import pexpect
  
  def auth(username, password):
      clean_username = re.sub('[^a-zA-Z0-9]', '_', username)
      cmd = [ 'su', '--login', '-c /bin/true', clean_username ]
  
      try:
          p = pexpect.spawn(' '.join(cmd), timeout=60)
          p.expect('.*assword.*')
          p.sendline(password)
          p.expect(pexpect.EOF)
          p.close()
  
          return p.exitstatus == 0    
      except:
          return False
  
subject: handle pexpect exception