title: How to use custom password validators beside the django auth password validators?
body: <p>As the question above mentioned, I will trying to use a certain extra rule to validate a password during the registration process. 
  The extra rule should be that a password is validate if it has at least one digit, one letter and one special character. </p>
  
  <p>My approach to solute this problem I've created a file named validators.py. </p>
  
  <pre><code>from django.core.exceptions import ValidationError
  
  class CustomPasswortValidator:
  
      def validate(value):
  
        # check for digit
        if not any(char.isdigit() for char in value):
            raise ValidationError(_('Password must contain at least 1 digit.'))
  
        # check for letter
        if not any(char.isalpha() for char in value):
            raise ValidationError(_('Password must contain at least 1 letter.'))
  
        # check for special character
        special_characters = "[~\!@#\$%\^&amp;\*\(\)_\+{}\":;'\[\]]"
        if not any(char in special_characters for char in value):
          raise ValidationError(_('Password must contain at least 1 letter.'))
  </code></pre>
  
  <p>My custom registration form looks like this: </p>
  
  <pre><code>from django import forms
  from django.contrib.auth.forms import UserCreationForm
  from django.contrib.auth.models import User
  
  
  class RegistrationForm(UserCreationForm):
      first_name = forms.CharField(max_length=30, required=False,                                         
                                   help_text='Optional.')
      last_name = forms.CharField(max_length=30, required=False, 
                                   help_text='Optional.')
      email = forms.EmailField(max_length=254, help_text='Required. Inform a valid email address.')
  
      class Meta:
          model = User
          fields = ('username', 'first_name', 'last_name', 'email', 'password1', 'password2', )
  </code></pre>
  
  <p>I don't get it how I tell django, that my custom password validator should be use beside the django AUTH_PASSWORD_VALIDATORS.</p>