i got error 500 on production when i read filefield in django

Question

hello everyone please help me i have recently maked a website but i got 500 error when i put it in production but strangly all is working well in my computer i am trying to read the buffer of a filefield inside a model and itson local but not in production

class post(models.Model):
titre=models.CharField(unique=True,null=True,max_length=100)
description=models.TextField(null=True,blank=True,max_length=400)
T=models.CharField(default="image",blank=True,max_length=50)
image=models.FileField(null=True)
cat=models.ForeignKey(categorie,on_delete=models.CASCADE,null=True)
datepost=models.DateTimeField(auto_now_add=True,blank=True)
user=models.ForeignKey(myuser,on_delete=models.CASCADE,null=True)
vue=models.IntegerField(default=0,blank=True)
def __str__(self):
    return self.titre

def save(self, *args ,**kwargs):
    #cette partie permet de generer un identifiant unique
    f=self.image.readline()
    mime=magic.from_buffer(f,mime=True)
    if "video" in mime :
        self.T="short"
    super(post,self).save(*args,**kwargs)

sorry for my english and thank you for your help