Add a test for pdb until command in coroutine (GH-5427) (#5428)

(cherry picked from commit 4f4ef0a)

Author: miss-islington

Lib/test/test_pdb.py

@@ -979,6 +979,52 @@ def test_pdb_until_command_for_generator():
     finished
     """
 
+def test_pdb_until_command_for_coroutine():
+    """Testing no unwindng stack for coroutines
+       for "until" command if target breakpoing is not reached
+
+    >>> import asyncio
+
+    >>> async def test_coro():
+    ...     print(0)
+    ...     await asyncio.sleep(0)
+    ...     print(1)
+    ...     await asyncio.sleep(0)
+    ...     print(2)
+    ...     await asyncio.sleep(0)
+    ...     print(3)
+
+    >>> async def test_main():
+    ...     import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+    ...     await test_coro()
+
+    >>> def test_function():
+    ...     loop = asyncio.new_event_loop()
+    ...     loop.run_until_complete(test_main())
+    ...     loop.close()
+    ...     print("finished")
+
+    >>> with PdbTestInput(['step',
+    ...                    'until 8',
+    ...                    'continue']):
+    ...     test_function()
+    > <doctest test.test_pdb.test_pdb_until_command_for_coroutine[2]>(3)test_main()
+    -> await test_coro()
+    (Pdb) step
+    --Call--
+    > <doctest test.test_pdb.test_pdb_until_command_for_coroutine[1]>(1)test_coro()
+    -> async def test_coro():
+    (Pdb) until 8
+    0
+    1
+    2
+    > <doctest test.test_pdb.test_pdb_until_command_for_coroutine[1]>(8)test_coro()
+    -> print(3)
+    (Pdb) continue
+    3
+    finished
+    """
+
 def test_pdb_next_command_in_generator_for_loop():
     """The next command on returning from a generator controlled by a for loop.