Check that notes correspond to someone in the jury, and throw an error if this is not the case

Signed-off-by: Emmy D'Anello <emmy.danello@animath.fr>

participation/views.py

@@ -810,10 +810,14 @@ class PoolUploadNotesView(VolunteerMixin, FormView, DetailView):
         pool = self.get_object()
         parsed_notes = form.cleaned_data['parsed_notes']
 
-        for vr, notes in parsed_notes.items():
+        for vr in parsed_notes.keys():
             if vr not in pool.juries.all():
                 form.add_error('file', _("The following user is not registered as a jury:") + " " + str(vr))
 
+        if form.errors:
+            return self.form_invalid(form)
+
+        for vr, notes in parsed_notes.items():
             # There is an observer note for 4-teams pools
             notes_count = 7 if pool.passages.count() == 4 else 6
             for i, passage in enumerate(pool.passages.all()):