'Checks for the identification and password.
If the combination can\'t be found will raise an invalid sign in error.'

def clean(self):

    identification = self.cleaned_data.get(u'identification')
    password = self.cleaned_data.get(u'password')
    if (identification and password):
        user = authenticate(identification=identification, password=password)
        if (user is None):
            raise forms.ValidationError(_(u'Please    enter    a    correct    username    or    email    and    password.    Note    that    both    fields    are    case-sensitive.'))
    return self.cleaned_data
