bpo-42183: Fix a stack overflow error for asyncio Task or Future repr() (GH-23020)

The overflow occurs under some circumstances when a task or future
recursively returns itself.

Co-authored-by: Kyle Stanley <aeros167@gmail.com>

Lib/test/test_asyncio/test_futures2.py

@@ -0,0 +1,18 @@
+# IsolatedAsyncioTestCase based tests
+import asyncio
+import unittest
+
+
+class FutureTests(unittest.IsolatedAsyncioTestCase):
+    async def test_recursive_repr_for_pending_tasks(self):
+        # The call crashes if the guard for recursive call
+        # in base_futures:_future_repr_info is absent
+        # See Also: https://bugs.python.org/issue42183
+
+        async def func():
+            return asyncio.all_tasks()
+
+        # The repr() call should not raise RecursiveError at first.
+        # The check for returned string is not very reliable but
+        # exact comparison for the whole string is even weaker.
+        self.assertIn('...', repr(await asyncio.wait_for(func(), timeout=10)))