Another fix for link_error signatures being dicts instead of `Sig…

…nature`s (#8841)

* Another fix for `link_error` signatures being `dict`s instead of `Signature`s

Related to #8678

* whitespace

* typo

* adding unittest

* typo

celery/canvas.py

@@ -1673,6 +1673,8 @@ def link_error(self, sig):
         #
         # We return a concretised tuple of the signatures actually applied to
         # each child task signature, of which there might be none!
+        sig = maybe_signature(sig)
+
         return tuple(child_task.link_error(sig.clone(immutable=True)) for child_task in self.tasks)
 
     def _prepared(self, tasks, partial_args, group_id, root_id, app,

t/unit/tasks/test_canvas.py

@@ -869,6 +869,16 @@ def test_link_error(self):
         for child_sig in g1.tasks:
             child_sig.link_error.assert_called_with(sig.clone(immutable=True))
 
+    def test_link_error_with_dict_sig(self):
+        g1 = group(Mock(name='t1'), Mock(name='t2'), app=self.app)
+        errback = signature('tcb')
+        errback_dict = dict(errback)
+        g1.link_error(errback_dict)
+        # We expect that all group children will be given the errback to ensure
+        # it gets called
+        for child_sig in g1.tasks:
+            child_sig.link_error.assert_called_with(errback.clone(immutable=True))
+
     def test_apply_empty(self):
         x = group(app=self.app)
         x.apply()