bpo-41332: Added missing connect_accepted_socket() to AbstractEventLoop (GH-21533)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>
Co-authored-by: Kyle Stanley <aeros167@gmail.com>
diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index 0dce87b..1a20f36 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -418,6 +418,20 @@ async def create_unix_server(
         """
         raise NotImplementedError
 
+    async def connect_accepted_socket(
+            self, protocol_factory, sock,
+            *, ssl=None,
+            ssl_handshake_timeout=None):
+        """Handle an accepted connection.
+
+        This is used by servers that accept connections outside of
+        asyncio, but use asyncio to handle connections.
+
+        This method is a coroutine.  When completed, the coroutine
+        returns a (transport, protocol) pair.
+        """
+        raise NotImplementedError
+
     async def create_datagram_endpoint(self, protocol_factory,
                                        local_addr=None, remote_addr=None, *,
                                        family=0, proto=0, flags=0,