'validate if email exist in database
from legacy register
return: raise error if it exist'

def clean(self, email):

    email = super(UserEmailField, self).clean(email.strip())
    if self.skip_clean:
        return email
    if (settings.EMAIL_UNIQUE == True):
        try:
            user = User.objects.get(email=email)
            raise forms.ValidationError(self.error_messages['taken'])
        except User.DoesNotExist:
            return email
        except User.MultipleObjectsReturned:
            raise forms.ValidationError(self.error_messages['taken'])
    else:
        return email
