title: string.isalpha() returning False under custom django validator whether string contains a number or not
body: <p>I am trying to use custom validation on a Django CharField model field. I'm checking whether the name has number in it. If it does, raise a <code>ValidationError</code>. I use the line <code>if name.isalpha() is False: raise ValidationError</code>. For some reason this equates to False whether there is a number present in the string or not. I checked to make sure that <code>name</code> was the value I was expecting it to be and that it was indeed a string. Here is my code:</p>
  
  <blockquote>
    <p>models.py</p>
  </blockquote>
  
  <pre><code>name = models.CharField(validators=[validate_name], max_length=100, default='', unique=True)
  </code></pre>
  
  <blockquote>
    <p>validation.py</p>
  </blockquote>
  
  <pre><code>from django.core.exceptions import ValidationError
  from django.utils.translation import gettext_lazy as _
  
  
  def validate_name(name):
      print(name.isalpha())
  
      if name.isalpha is False:
          raise ValidationError(
              _('Name can only contain letters A-Z. Not numbers.'),
              params={'name': name},
          )
  </code></pre>