Issue #20400: Merge Tulip into Python: add the new asyncio.subprocess module

* Add a new asyncio.subprocess module
* Add new create_subprocess_exec() and create_subprocess_shell() functions
* The new asyncio.subprocess.SubprocessStreamProtocol creates stream readers
  for stdout and stderr and a stream writer for stdin.
* The new asyncio.subprocess.Process class offers an API close to the
  subprocess.Popen class:

  - pid, returncode, stdin, stdout and stderr attributes
  - communicate(), wait(), send_signal(), terminate() and kill() methods

* Remove STDIN (0), STDOUT (1) and STDERR (2) constants from base_subprocess
  and unix_events, to not be confused with the symbols with the same name of
  subprocess and asyncio.subprocess modules
* _ProactorBasePipeTransport.get_write_buffer_size() now counts also the size
  of the pending write
* _ProactorBaseWritePipeTransport._loop_writing() may now pause the protocol if
  the write buffer size is greater than the high water mark (64 KB by default)

1 files changed, 7 insertions, 8 deletions

diff --git a/Lib/test/test_asyncio/test_base_events.py b/Lib/test/test_asyncio/test_base_events.py
index 1db7723..72f5c8a 100644
--- a/Lib/test/test_asyncio/test_base_events.py
+++ b/Lib/test/test_asyncio/test_base_events.py
@@ -116,18 +116,17 @@ class BaseEventLoopTests(unittest.TestCase):
             self.loop.stop()
 
         self.loop._process_events = unittest.mock.Mock()
-        delay = 0.1
-
-        when = self.loop.time() + delay
+        when = self.loop.time() + 0.1
         self.loop.call_at(when, cb)
         t0 = self.loop.time()
         self.loop.run_forever()
         dt = self.loop.time() - t0
-
-        self.assertGreaterEqual(dt, delay - self.loop._granularity, dt)
-        # tolerate a difference of +800 ms because some Python buildbots
-        # are really slow
-        self.assertLessEqual(dt, 0.9, dt)
+        self.assertTrue(0.09 <= dt <= 0.9,
+                        # Issue #20452: add more info in case of failure,
+                        # to try to investigate the bug
+                        (dt,
+                         self.loop._granularity,
+                         time.get_clock_info('monotonic')))
 
     def test_run_once_in_executor_handle(self):
         def cb():