Issue #15759: "make suspicious", "make linkcheck" and "make doctest" in Doc/
now display special message when and only when there are failures.
Merge heads
Fixed bugs in reprs of CookieJar and multiprocessing.dummy.Value.
asyncio, tulip issue 193: Convert StreamWriter.drain() to a classic coroutine

Replace also _make_drain_waiter() function with a classic _drain_helper()
coroutine.