Add a comment to emphasise why we shouldn't break the HomepageForm.

(imported from commit 1b4d59e0c868e8350d2a9eb46cdfdaed1f34e69f)

zephyr/forms.py

@@ -46,6 +46,8 @@ class ToSForm(forms.Form):
     terms = forms.BooleanField(required=True)
 
 class HomepageForm(forms.Form):
+    # This form is sort of important, because it determines whether users
+    # can register for our product. Be careful when modifying the validators.
     if settings.ALLOW_REGISTER:
         email = forms.EmailField()
     else: