title: Django Error: "You are trying to add a non-nullable field 'author' to entry without a default"
body: <p>I was trying to make migrations after adding an author field in my models.py file but Django asked me this:</p>
  
  <pre><code>You are trying to add a non-nullable field 'author' to entry without a default; we can't do that (the database needs something to populate existing rows).
  Please select a fix:
   1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
   2) Quit, and let me add a default in models.py
  </code></pre>
  
  <p>My Models.py File:</p>
  
  <pre><code>from django.db import models
  from django.utils import timezone
  from django.urls import reverse
  from django.contrib.auth.models import User
  
  
  class Entry(models.Model):
      title = models.CharField(max_length=50, default=timezone.now)
      date = models.DateTimeField(default=timezone.now)
      content = models.TextField()
      author = models.ForeignKey(User, on_delete=models.CASCADE)
  
      def get_absolute_url(self):
          return reverse('diary:index')
  
      def __str__(self):
          return self.title
  </code></pre>
  
  <p>I wanted to add the user who's currently active as the author, so I did this on my views.py file:</p>
  
  <pre><code>class EntryCreate(CreateView):
      model = Entry
      fields = ['title', 'content']
  
      def form_valid(self, form):
          form.instance.author = self.request.author
          return super().form_valid(form)
  </code></pre>
  
  <p>What Should I Do To Avoid This?</p>
  
  <p>Thanks In Advance!</p>