Merge tag 'v1.26.0rc2' into develop

Synapse 1.26.0rc2 (2021-01-25)
==============================

Bugfixes
--------

- Fix receipts and account data not being sent down sync. Introduced in v1.26.0rc1. ([\#9193](https://github.com/matrix-org/synapse/issues/9193), [\#9195](https://github.com/matrix-org/synapse/issues/9195))
- Fix chain cover update to handle events with duplicate auth events. Introduced in v1.26.0rc1. ([\#9210](https://github.com/matrix-org/synapse/issues/9210))

Internal Changes
----------------

- Add an `oidc-` prefix to any `idp_id`s which are given in the `oidc_providers` configuration. ([\#9189](https://github.com/matrix-org/synapse/issues/9189))
- Bump minimum `psycopg2` version to v2.8. ([\#9204](https://github.com/matrix-org/synapse/issues/9204))

tests/util/test_itertools.py

@@ -92,3 +92,15 @@ class SortTopologically(TestCase):
         # Valid orderings are `[1, 3, 2, 4]` or `[1, 2, 3, 4]`, but we should
         # always get the same one.
         self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])
+
+    def test_duplicates(self):
+        "Test that a graph with duplicate edges work"
+        graph = {1: [], 2: [1, 1], 3: [2, 2], 4: [3]}  # type: Dict[int, List[int]]
+
+        self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])
+
+    def test_multiple_paths(self):
+        "Test that a graph with multiple paths between two nodes work"
+        graph = {1: [], 2: [1], 3: [2], 4: [3, 2, 1]}  # type: Dict[int, List[int]]
+
+        self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])