asyncio, Tulip issue 157: Improve test_events.py, avoid run_briefly() which is

not reliable

Lib/asyncio/test_utils.py

@@ -21,10 +21,11 @@ try:
 except ImportError:  # pragma: no cover
     ssl = None
 
-from . import tasks
 from . import base_events
 from . import events
+from . import futures
 from . import selectors
+from . import tasks
 
 
 if sys.platform == 'win32':  # pragma: no cover
@@ -52,18 +53,14 @@ def run_briefly(loop):
         gen.close()
 
 
-def run_until(loop, pred, timeout=None):
-    if timeout is not None:
-        deadline = time.time() + timeout
+def run_until(loop, pred, timeout=30):
+    deadline = time.time() + timeout
     while not pred():
         if timeout is not None:
             timeout = deadline - time.time()
             if timeout <= 0:
-                return False
-            loop.run_until_complete(tasks.sleep(timeout, loop=loop))
-        else:
-            run_briefly(loop)
-    return True
+                raise futures.TimeoutError()
+        loop.run_until_complete(tasks.sleep(0.001, loop=loop))
 
 
 def run_once(loop):