title: Multiple primary keys for table "app_employee" are not allowed.
body: <p>Django 1.11 with PostgreSQL. </p>
  
  <p>I go to migrate my site and <code>models.py</code> throws the error that I can't have more than one primary key. I can't see where I do (or I'm not understanding how). </p>
  
  <pre><code>class Employee(models.Model):
      Aegis_ID = models.UUIDField(primary_key=True, null=False, default=uuid.uuid4, editable=False, serialize=True)
      Employee_Number = models.ForeignKey('self', on_delete=models.CASCADE, related_name='Company_Employee_Number', 
                                      null=True, blank=True, max_length=6, help_text="Employee ID")
      Employee_FName = models.CharField(null=True, blank=True, max_length=25, help_text="First Name")
      Employee_LName = models.CharField(null=True, blank=True, max_length=25, help_text="Last Name")
      Employee_Email = models.EmailField(max_length=80, blank=True, help_text="GPM Email address")
      Employee_Position = models.ForeignKey('self', on_delete=models.CASCADE, null=True, blank=True, 
                                        related_name='Department_Employee_Position', max_length=3, 
                                        choices=EMPLOYEE_POSITION, help_text="Select position of this Employee.")
      Hire_Date = models.DateField(null=True, blank=True, help_text="Enter the employee hire date.")
      Employee_Division = models.CharField(max_length=2, null=True, blank=True, choices=DIVISION_CHOICES,
                                       help_text="Assign the Audit Division for this employee.")
      Employee_Region = models.CharField(max_length=3, null=True, blank=True, choices=REGION_CHOICES,
                                     help_text="Assign the Audit Region for this employee.")
      Employee_District = models.CharField(max_length=3, null=True, blank=True, choices=DISTRICT_CHOICES,
                                       help_text="Assign the Audit District for this Employee.")
  </code></pre>
  
  <p>Reading the Django pages on this exact topic, it's listed as a problem resolved in 1.7 and had to do with how Django sorted the tables by class, alphabetically. </p>
  
  <p>I've also tried <code>python manage.py flush</code> followed by <code>makemigrations</code> prior to <code>migrate</code></p>
  
  <p>So, what fields is Django / Postgres attempting to make an "id" and "primary" because I'm just not understanding, here...</p>
  
  <p>According to the Django documentation regarding Automatic Primary Keys, there's the unseen is <code>id = models.AutoField(primary_key=True)</code> but I also understood that if you assign the <code>primary_key=True</code> to a field, this did not apply</p>