* _UnixSubprocessTransport: fix file mode of stdin. Open stdin in write mode,
  not in read mode
* Examples: close the event loop at exit
* More reliable CoroWrapper.__del__. If the constructor is interrupted by
  KeyboardInterrupt or the coroutine objet is destroyed lately, some the
  _source_traceback attribute doesn't exist anymore.
* repr(Task): include also the future the task is waiting for

it ignored I/O errors if at least the first C call read() succeed.

ssl.RAND_add() now supports strings longer than 2 GB.

size_t, because %zi/%u is not supported on all platforms.

to remove duplication and return info for tests.  Rewrite corresponding tests.
Test_create_option_buttons was not testing anything because of buggy
comparisons.  Use Python subscripting to get widget options.

either deleting or moving to the module's main function.

don't log the "destroy pending task" message anymore. The log is redundant for
run_until_complete() and useless in run_briefly().

- Sort imports
- Simplify/optimize iscoroutine(). Inline inspect.isgenerator(obj): replace it
  with isinstance(obj, types.GeneratorType)
- CoroWrapper: check at runtime if Python has the yield-from bug #21209.  If
  Python has the bug, check if CoroWrapper.send() was called by yield-from to
  decide if parameters must be unpacked or not.
- Fix "Task was destroyed but it is pending!" warning in
  test_task_source_traceback()

Reported by Krishna Kumar Thakur on docs@.

getbufferproc().

object is destroyed. The destructor now closes the file if needed. The close()
method can now be called twice: the second call does nothing.

- Use support.captured_stderr() where appropriate
- Removes some "from test.support import xxx" import and uses support.xxx
  instead.

Handle objects are created. Pass the traceback to call_exception_handler() in
the 'source_traceback' key.

The traceback is truncated to hide internal calls in asyncio, show only the
traceback from user code.

Add tests for the new source_traceback, and a test for the 'Future/Task
exception was never retrieved' log.

object was created to the "coroutine ... was never yield from" log

This makes the behavior match that of Parser.  Patch by Vajrasky Kok.