First working version of the code.

password_required/forms.py

@@ -0,0 +1,45 @@
+from django import forms
+from django.conf import settings
+from django.utils.translation import ugettext_lazy as _
+
+class AuthenticationForm(forms.Form):
+    """
+    Simple form to allow users to access a page via a password.
+
+    A copy of django.contrib.auth.forms.AuthenticationForm, adapted to this
+    much simpler use case.
+    """
+    password = forms.CharField(label=_("Password"), widget=forms.PasswordInput)
+
+    def __init__(self, request=None, *args, **kwargs):
+        """
+        If request is passed in, the form will validate that cookies are
+        enabled. Note that the request (a HttpRequest object) must have set a
+        cookie with the key TEST_COOKIE_NAME and value TEST_COOKIE_VALUE before
+        running this validation.
+        """
+        self.request = request
+        super(AuthenticationForm, self).__init__(*args, **kwargs)
+
+
+    def clean(self):
+        """
+        Validate that the password entered was correct.
+        """
+        password = self.cleaned_data.get('password')
+        correct_password = getattr(settings, 'PASSWORD_REQUIRED_PASSWORD', None)
+
+        if not correct_password:
+            raise forms.ValidationError(_("PASSWORD_REQUIRED_PASSWORD is not set, and thus it is currently impossible to log in."))
+
+        if not (password == correct_password or
+                password.strip() == correct_password):
+            raise forms.ValidationError(_("Please enter the correct password. Note that the password is case-sensitive."))
+
+        # TODO: determine whether this should move to its own method.
+        if self.request:
+            if not self.request.session.test_cookie_worked():
+                raise forms.ValidationError(_("Your Web browser doesn't appear to have cookies enabled. Cookies are required for logging in."))
+
+        return self.cleaned_data
+