Add a preference to allow reply speakers without substantives

Closes TabbycatDebate#1584

tabbycat/options/preferences.py

@@ -493,6 +493,15 @@ class ReplyScores(BooleanPreference):
     default = True
 
 
+@tournament_preferences_registry.register
+class RequireSubstantiveForReply(BooleanPreference):
+    help_text = _("Whether to limit reply speeches to speakers who gave a constructive speech in the debate")
+    verbose_name = _("Require reply speaker to have given a substantive speech")
+    section = debate_rules
+    name = 'require_substantive_for_reply'
+    default = True
+
+
 @tournament_preferences_registry.register
 class MotionVetoes(BooleanPreference):
     help_text = _("Enables the motion veto field on ballots, to track veto statistics")

tabbycat/results/forms.py

@@ -507,7 +507,7 @@ def clean_speakers(self, cleaned_data):
                     ))
 
                 # The reply speaker must have given a substantive speech.
-                if len(speaker_positions.get(reply_speaker, [])) == 0:
+                if self.tournament.pref('require_substantive_for_reply') and len(speaker_positions.get(reply_speaker, [])) == 0:
                     self.add_error(self._fieldname_speaker(side, self.reply_position), forms.ValidationError(
                         _("The reply speaker for this team did not give a substantive speech."),
                         code='reply_speaker_not_repeat',