Fix template validator function.

ticdesk_events/forms.py

@@ -25,13 +25,15 @@ def is_phonenumber(number):
         raise forms.ValidationError(_('%s ist keine gültige Telefonnummer!') % number)
 
 def clean_phonenumber(obj, field):
-    value = obj.cleaned_data[field]
+    def _clean_phonenumber(obj):
+        value = obj.cleaned_data[field]
 
-    if value:
-        pn = phonenumbers.parse(pn, 'DE')
-        value = phonenumbers.format_number(pn, phonenumbers.PhoneNumberFormat.E164)
+        if value:
+            pn = phonenumbers.parse(pn, 'DE')
+            value = phonenumbers.format_number(pn, phonenumbers.PhoneNumberFormat.E164)
 
-    return value
+        return value
+    return _clean_phonenumber
 
 class EventRegisterForm(forms.Form):
     cn = forms.CharField(label=_('Dein Name'), disabled=True)