* 'master' of https://github.com/python/cpython: (601 commits)
  remove check for bug last seem in Solaris 9 (python#3285)
  Change code owners for hashlib and ssl to the crypto team (python#3284)
  bpo-31281: Fix pathlib.Path incompatibility in fileinput (pythongh-3208)
  remove autoconf check for select() (python#3283)
  remove configure check for 'volatile' (python#3281)
  Add missing _sha3 module to Setup.dist (python#2395)
  bpo-12383: Also ignore __PYVENV_LAUNCHER__ (python#3278)
  bpo-9146: add the missing NEWS entry. (python#3275)
  Fix a c.f.as_completed() refleak previously introduced in bpo-27144 (python#3270)
  bpo-31185: Fixed miscellaneous errors in asyncio speedup module. (python#3076)
  remove a redundant lower in urllib.parse.urlsplit (python#3008)
  bpo-31323: Fix reference leak in test_ssl (python#3263)
  bpo-31250, test_asyncio: fix EventLoopTestsMixin.tearDown() (python#3264)
  bpo-31326: ProcessPoolExecutor waits for the call queue thread (python#3265)
  bpo-27144: concurrent.futures as_complete and map iterators do not keep reference to returned object (python#1560)
  bpo-31250, test_asyncio: fix dangling threads (python#3252)
  bpo-31217: Fix regrtest -R for small integer (python#3260)
  bpo-30096: Use ABC in abc reference examples (python#1220)
  bpo-30737: Update DevGuide links to new URL (pythonGH-3228)
  [Trivial] Remove now redundant assert (python#3245)
  ...

Store exceptions as string rather than object to prevent reference
cycles which cause leaking dangling threads.

Store exceptions as string rather than object to prevent reference
cycles which cause leaking dangling threads.
(cherry picked from commit 8687101)

Store exceptions as string rather than object to prevent reference
cycles which cause leaking dangling threads.
(cherry picked from commit 8687101)