Программна выдает ошибку 'NoneType' object has no attribute 'ljust'

import RPi.GPIO as GPIO
import os
import socket
import fcntl
import struct
import time
from time import gmtime, strftime
 
def getCPUtemperature():
  res = os.popen("vcgencmd measure_temp").readline()
  return(res.replace("temp=","").replace("'C\n",""))
 
def printDateTime():
  textDate = strftime("%d %A %Y", gmtime())
  textTime = strftime("%H:%M:%S", gmtime())
  lcd_string(textDate,LCD_LINE_1)
  lcd_string(textTime,LCD_LINE_2)
  return
 
def getInterfaceAddress(ifname):
  try:
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
      s.fileno(),
      0x8915,  # SIOCGIFADDR
      struct.pack('256s', ifname[:15])
    )[20:24])
  except:
    return ''
 
def getIP():
  ipWlan = getInterfaceAddress('wlan0')
  if ipWlan:
    return ipWlan
  ipEth = getInterfaceAddress('eth0')
  if ipEth:
    return ipEth
 
# Распиновка дисплея
LCD_RS = 7
LCD_E  = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18
 
 
LCD_WIDTH = 16    # Ширина строки дисплея
LCD_CHR = True
LCD_CMD = False
 
LCD_LINE_1 = 0x80 # LCD RAM адрес первой строки
LCD_LINE_2 = 0xC0 # LCD RAM адрес второй строки
 
E_PULSE = 0.0005
E_DELAY = 0.0005
 
def main():
    
  GPIO.setwarnings(False)
  GPIO.setmode(GPIO.BCM)       # 
  GPIO.setup(LCD_E, GPIO.OUT)  # E
  GPIO.setup(LCD_RS, GPIO.OUT) # RS
  GPIO.setup(LCD_D4, GPIO.OUT) # DB4
  GPIO.setup(LCD_D5, GPIO.OUT) # DB5
  GPIO.setup(LCD_D6, GPIO.OUT) # DB6
  GPIO.setup(LCD_D7, GPIO.OUT) # DB7
 
 
  # Инициализация дисплея
  lcd_init()
 
  while True:
 
    # Дата и время
    index = 0
    while index < 5:
      printDateTime()
      time.sleep(1)
      index += 1
 
    # Температура ЦП
    lcd_string("CPU temperature:",LCD_LINE_1)
    textCPU = getCPUtemperature()+"C"
    lcd_string(textCPU,LCD_LINE_2)
 
    time.sleep(3)
 
   
    lcd_string("IP:",LCD_LINE_1)
    textIP = getIP()
    lcd_string(textIP,LCD_LINE_2)
 
    time.sleep(3)
 
def lcd_init():
  # Инициализация дисплея
  lcd_byte(0x33,LCD_CMD) # 110011
  lcd_byte(0x32,LCD_CMD) # 110010 
  lcd_byte(0x06,LCD_CMD) # 000110
  lcd_byte(0x0C,LCD_CMD) # 001100 
  lcd_byte(0x28,LCD_CMD) # 101000 
  lcd_byte(0x01,LCD_CMD) # 000001 
  time.sleep(E_DELAY)
 
def lcd_byte(bits, mode):
  
  GPIO.output(LCD_RS, mode) 
    GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)
 
    lcd_toggle_enable()
 
  
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)
 
 
  lcd_toggle_enable()
 
def lcd_toggle_enable():
 
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)
 
def lcd_string(message,line):
  
 
  message = message.ljust(LCD_WIDTH," ")
 
  lcd_byte(line, LCD_CMD)
 
  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)
 
if __name__ == '__main__':
 
  try:
    main()
  except KeyboardInterrupt:
    pass
  finally:
    lcd_byte(0x01, LCD_CMD)
    lcd_string("Goodbye!",LCD_LINE_1)
    GPIO.cleanup()

Traceback (most recent call last):
  File "ll.py", line 228, in <module>
    main()
  File "ll.py", line 148, in main
    lcd_string(textIP,LCD_LINE_2)
  File "ll.py", line 218, in lcd_string
    message = message.ljust(LCD_WIDTH," ")
AttributeError: 'NoneType' object has no attribute 'ljust'