Global name 'system' is not defined

Ignition
7

I have the same error with the gateway event script - Tag Change below :

import StringIO
import csv
import os
import ftplib
import sys
import system
from datetime import date
from datetime import datetime
from datetime import timedelta

if newValue.value==0:
	sys.exit()

today=date.today() #Récupère la date du jour au format 'aaaa-mm-jj'
datejour= str(today).replace('-','') #Remplace les - par rien
yesterday=date.today() - timedelta(days=1) #Récupère la date de la veille
yesterday_jour=str(yesterday).replace('-','') #Remplace les - par rien
#print datejour,yesterday_jour


ftp = ftplib.FTP('myip') 
ftp.login('user','password')
files = [] #créé liste vide
ftp.retrlines('NLST', files.append) #Récupère la liste des fichiers dans le dossier du FTP et alimente la liste

#print files

def callback(buf):
	ftmp=system.file.getTempFile("data")
	#print ftmp
	
	f=open(ftmp, 'wb')
	f.write(buf)
	system.file.writeFile("C:\\TempTest\\NewTest.data",buf)
	#print buf
	
	dataIn=	StringIO.StringIO(buf)
	reader=csv.reader(dataIn, delimiter=';', quotechar="\"")
	dataOut=[]
	headers=["Poste","Nom","Date","DJU"]
	for row in reader:
		dataOut.append(row)
	#print dataOut
	
	date=datetime.strptime(dataOut[-1][2]+'000000','%Y%m%d%H%M%S')
	dju=dataOut[-1][3].replace(',','.')
	#print dataOut[-1][2], dju,date
	
	
	f.close()
	
	query="INSERT INTO dju (t_stamp,dju) VALUES (?,?)"
	system.db.runPrepUpdate(query,[date,dju])


filename="DJU_"+yesterday_jour+".data"
#print filename
ftp.retrbinary('RETR '+filename, callback)
ftp.voidcmd('QUIT')
ftp.close()

Thanks