Validates that the val is in the list of values for this Enum.

        Returns two element tuple: (bool, string)

        - `bool` - True if valid, False if not
        - `string` - Description of validation error, or None if valid

        :Parameters:
          val
            Value to validate.  Should be a string.

def validate(self, val):
        """
        Validates that the val is in the list of values for this Enum.

        Returns two element tuple: (bool, string)

        - `bool` - True if valid, False if not
        - `string` - Description of validation error, or None if valid

        :Parameters:
          val
            Value to validate.  Should be a string.
        """
        if val in self.values:
            return True, None
        else:
            return False, "'%s' is not in enum: %s" % (val, str(self.values))