bpo-36046: Fix buildbot failures (GH-16091)

Varying user/group/permission check needs on platforms.

Author: gpshead

Lib/test/test_subprocess.py

@@ -1588,6 +1588,18 @@ def test_run_with_shell_timeout_and_capture_output(self):
  f"{stacks}```")
 
 
+def _get_test_grp_name():
+ for name_group in ('staff', 'nogroup', 'grp'):
+ if grp:
+ try:
+ grp.getgrnam(name_group)
+ except KeyError:
+ continue
+ return name_group
+ else:
+ raise unittest.SkipTest('No identified group name to use for this test on this platform.')
+
+
 @unittest.skipIf(mswindows, "POSIX specific tests")
 class POSIXProcessTestCase(BaseTestCase):
 
@@ -1762,8 +1774,10 @@ def test_user(self):
  [sys.executable, "-c",
  "import os; print(os.getuid())"],
  user=user)
+ except PermissionError: # errno.EACCES
+ pass
  except OSError as e:
- if e.errno != errno.EPERM:
+ if e.errno not in (errno.EACCES, errno.EPERM):
  raise
  else:
  if isinstance(user, str):
@@ -1789,7 +1803,7 @@ def test_user_error(self):
  def test_group(self):
  gid = os.getegid()
  group_list = [65534 if gid != 65534 else 65533]
- name_group = "nogroup" if sys.platform != 'darwin' else "staff"
+ name_group = _get_test_grp_name()
 
  if grp is not None:
  group_list.append(name_group)
@@ -1830,7 +1844,7 @@ def test_group_error(self):
  def test_extra_groups(self):
  gid = os.getegid()
  group_list = [65534 if gid != 65534 else 65533]
- name_group = "nogroup" if sys.platform != 'darwin' else "staff"
+ name_group = _get_test_grp_name()
  perm_error = False
 
  if grp is not None: