detect and handle task cancellations semi-properly

respodns/dns.py

@@ -113,7 +113,7 @@ def process_result(res, ip, check, opts: Options):
 
 async def try_ip(db, server_ip, checks, opts: Options):
     from .util import make_pooler
-    from asyncio import sleep
+    from asyncio import sleep, CancelledError
 
     entries = []
     deferred = []
@@ -130,7 +130,11 @@ async def try_ip(db, server_ip, checks, opts: Options):
     def finisher(done, pending):
         nonlocal success
         for task in done:
-            res, ip, check = task.result()
+            try:
+                res, ip, check = task.result()
+            except CancelledError:
+                success = False
+                break
             entry = process_result(res, ip, check, opts)
             map(maybe_put_ip, entry.addrs)
             entries.append(entry)