title: Django regex validator message has no effect
body: <p>I am trying to get it so that the validator tells you "username must be alphanumeric". This is my code so far. I have confirmed that it validates at the correct time. The only problem is that no matter what I try, The RegexValidator still chucks the default error ("enter a valid value").</p>
  
  <p>This is my code. I also tried it without the 'message=' in front, and it still said "enter a valid value", instead of "username must be alphanumeric"</p>
  
  <pre><code>user = CharField(
      max_length=30,required=True,
      validators=[
          RegexValidator('^[a-zA-Z0-9]*$',
              message='Username must be Alphanumeric'
          ),
      ]
  )
  </code></pre>