leader not multi is not allowed

tests/dictionaries/80leadership_leader_not_multi/00-base.xml

@@ -0,0 +1,22 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<rougail>
+    <variables>
+        <family name="general">
+            <variable name="mode_conteneur_actif" type="oui/non" description="No change">
+                <value>non</value>
+            </variable>
+        </family>
+        <family name="general1">
+            <variable name="leader" type="string" description="leader"/>
+            <variable name="follower1" type="string" description="follower1"/>
+            <variable name="follower2" type="string" description="follower2"/>
+        </family>
+    </variables>
+
+    <constraints>
+        <group leader="leader">
+            <follower>follower1</follower>
+            <follower>follower2</follower>
+        </group>
+    </constraints>
+</rougail>