Get the real thread of an article

Side effect: fix the bug of incorrect date by using boobmsg show

weboob/tools/capabilities/messages/GenericBackend.py

@@ -40,12 +40,17 @@ class GenericNewspaperBackend(BaseBackend, ICapMessages):
     URL2ID = None
     RSSSIZE = 0
 
+    def _get_thread(self, id):
+        for thread in self.iter_threads():
+            if thread.id == id:
+                return thread
+
     def get_thread(self, _id):
         if isinstance(_id, Thread):
             thread = _id
             id = thread.id
         else:
-            thread = None
+            thread = self._get_thread(_id)
             id = _id
 
         with self.browser: