allow new registration only once

core/views/user_registration.py

@@ -181,6 +181,9 @@ def write_users(registered_users, encryptedfile, git_string):
     return True
 
 class newregister_form(forms.Form):  # not a model-form, just a form-form
+    """This is the form for a new user who has not been on expo before and 
+    does notalready have a username
+    """
     fullname = forms.CharField(strip=True, required=True, 
         label="Forename Surname",
         widget=forms.TextInput(
@@ -196,14 +199,22 @@ class newregister_form(forms.Form):  # not a model-form, just a form-form
 
     def clean(self):
         cleaned_data = super().clean()
-        un = cleaned_data.get("fullname") 
-            
+        fullname = cleaned_data.get("fullname")            
         email = cleaned_data.get("email")
+        
         users = User.objects.filter(email=email)
         if len(users) != 0:
             raise ValidationError(
                 "Duplicate email address. Another registered user is already using this email address. Email addresses must be unique as that is how we reset forgotten passwords."
             )  
+        userslug = troggle_slugify(fullname)
+        people = Person.objects.filter(slug=userslug)
+        if len(people) != 0:
+            raise ValidationError(
+                "Duplicate name. There is already a username correspondng to this Forename Surname. " +
+                "If you have been on expo before, you need to use the other form at expo.survex.com/accounts/register/ ." +
+             )  
+
             
 class register_form(forms.Form):  # not a model-form, just a form-form
     username = forms.CharField(strip=True, required=True,