Django custom login page
<p>I have a custom Django login page. I want to throw an exception when username or password fields are empty. How can I do that?</p>

<p>My view.py log in method :</p>

<pre><code>def user_login(request):
    context = RequestContext(request)
    if request.method == 'POST':
        # Gather the username and password provided by the user.
        # This information is obtained from the login form.
        username = request.POST['username']
        password = request.POST['password']
        user = authenticate(username=username, password=password)
        print("auth",str(authenticate(username=username, password=password)))

        if user:
            # Is the account active? It could have been disabled.
            if user.is_active:
                login(request, user)
                return HttpResponseRedirect('/')
        else:
            return HttpResponse("xxx.")
    else:
        # Bad login details were provided. So we can't log the user in.
        print ("Invalid login details: {0}, {1}".format(username, password))
        return HttpResponse("Invalid login details supplied.")
    else:
        return render_to_response('user/profile.html', {}, context)
</code></pre>

<p>I tried this and it didn't work:
This is forms.py</p>

<pre><code>def clean_username(self):
    username = self.cleaned_data.get('username')
    if not username:
        raise forms.ValidationError('username does not exist.')
</code></pre>