charfield primary key contentype error

Hi, I have a problem with a charfield foreign key. this my model

class Region(models.Model):
    """ Class décrivant la table Region """
    code_region = models.CharField(max_length=15, primary_key=True)
    name = models.CharField(max_length=25,null=True,blank=True)  
   
   
class Departement(models.Model):
    """ Class décrivant la table Département """
    code_dept = models.CharField(max_length=15, primary_key=True)
    name = models.CharField(max_length=25,null=True,blank=True)
    region = models.ForeignKey(Region, null=True,blank=True)

when i sync the database i have this error

django.contrib.contenttypes.models.DoesNotExist: ContentType matching query does not exist.

 what is the meaning of this error and how can i solve it?

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