class LoginForm(forms.Form):
    log_username = forms.CharField(required=True,min_length=5,label="E-mail")
    password = forms.CharField( widget=forms.PasswordInput(render_value=False), label="Hasło",min_length=6,required=True),

    def clean(self):
        username = request.POST['log_username']
        password = request.POST['password']
        user = authenticate(username=username, password=password)
        if user is None:
            raise forms.ValidationError((u'Cos zle wpisales.'))
        return self.cleaned_data