title: fields.E304 Reverse accessor clashes in Django
body: <p>I am trying to migrate these two models:</p>
  
  <pre><code># models.py
  
  from django.db import models
  
  
  class Person(models.Model):
      name = models.CharField(max_length=64)
  
  
  class Person2Person(models.Model):
      person = models.ForeignKey(Person)
      friend = models.ForeignKey(Person)
  </code></pre>
  
  <p>But I have got this error:</p>
  
  <pre><code>SystemCheckError: System check identified some issues:
  
  ERRORS:
  website.Person2Person.friend: (fields.E304) Reverse accessor for 'Person2Person.friend' clashes with reverse accessor for 'Person2Person.person'.
      HINT: Add or change a related_name argument to the definition for 'Person2Person.friend' or 'Person2Person.person'.
  website.Person2Person.person: (fields.E304) Reverse accessor for 'Person2Person.person' clashes with reverse accessor for 'Person2Person.friend'.
      HINT: Add or change a related_name argument to the definition for 'Person2Person.person' or 'Person2Person.friend'.
  </code></pre>
  
  <p>I want to make a relationship many-to-many in the model <code>Person</code>. Why is my code wrong? And how should I fix it?</p>