bpo-35491: Enhance multiprocessing.BaseProcess.__repr__() (GH-11138)

* Add the pid and parent pid to multiprocessing.BaseProcess.__repr__().
* Add negative sign (ex: "-SIGTERM") to exitcode (process killed
  by a signal)
* Only call _popen.poll() once.

Example:
  <ForkProcess(ForkPoolWorker-1, started daemon)>
becomes:
  <ForkProcess name='ForkPoolWorker-1' pid=12449 parent=12448 started daemon>

Example:
  <ForkProcess(ForkPoolWorker-1, stopped[SIGTERM] daemon)>
becomes:
  <ForkProcess name='ForkPoolWorker-1' pid=12960 parent=12959 stopped exitcode=-SIGTERM daemon>

1 files changed, 3 insertions, 3 deletions

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 578b548..1d0920a 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -626,14 +626,14 @@ The :mod:`multiprocessing` package mostly replicates the API of the
        >>> import multiprocessing, time, signal
        >>> p = multiprocessing.Process(target=time.sleep, args=(1000,))
        >>> print(p, p.is_alive())
-       <Process(..., initial)> False
+       <Process ... initial> False
        >>> p.start()
        >>> print(p, p.is_alive())
-       <Process(..., started)> True
+       <Process ... started> True
        >>> p.terminate()
        >>> time.sleep(0.1)
        >>> print(p, p.is_alive())
-       <Process(..., stopped[SIGTERM])> False
+       <Process ... stopped exitcode=-SIGTERM> False
        >>> p.exitcode == -signal.SIGTERM
        True