bpo-40275: Use new test.support helper submodules in tests (GH-21169)

diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index aced876..0162424 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -1,6 +1,9 @@
 import unittest
 from unittest import mock
 from test import support
+from test.support import import_helper
+from test.support import os_helper
+from test.support import warnings_helper
 import subprocess
 import sys
 import signal
@@ -20,7 +23,7 @@
 import gc
 import textwrap
 import json
-from test.support import FakePath
+from test.support.os_helper import FakePath
 
 try:
     import _testcapi
@@ -357,7 +360,7 @@
         # Normalize an expected cwd (for Tru64 support).
         # We can't use os.path.realpath since it doesn't expand Tru64 {memb}
         # strings.  See bug #1063571.
-        with support.change_cwd(cwd):
+        with os_helper.change_cwd(cwd):
             return os.getcwd()
 
     # For use in the test_cwd* tests below.
@@ -406,7 +409,7 @@
         # is relative.
         python_dir, python_base = self._split_python_path()
         rel_python = os.path.join(os.curdir, python_base)
-        with support.temp_cwd() as wrong_dir:
+        with os_helper.temp_cwd() as wrong_dir:
             # Before calling with the correct cwd, confirm that the call fails
             # without cwd and with the wrong cwd.
             self.assertRaises(FileNotFoundError, subprocess.Popen,
@@ -423,7 +426,7 @@
         python_dir, python_base = self._split_python_path()
         rel_python = os.path.join(os.curdir, python_base)
         doesntexist = "somethingyoudonthave"
-        with support.temp_cwd() as wrong_dir:
+        with os_helper.temp_cwd() as wrong_dir:
             # Before calling with the correct cwd, confirm that the call fails
             # without cwd and with the wrong cwd.
             self.assertRaises(FileNotFoundError, subprocess.Popen,
@@ -441,7 +444,7 @@
         python_dir, python_base = self._split_python_path()
         abs_python = os.path.join(python_dir, python_base)
         rel_python = os.path.join(os.curdir, python_base)
-        with support.temp_dir() as wrong_dir:
+        with os_helper.temp_dir() as wrong_dir:
             # Before calling with an absolute path, confirm that using a
             # relative path fails.
             self.assertRaises(FileNotFoundError, subprocess.Popen,
@@ -1052,7 +1055,7 @@
         try:
             for i in range(max_handles):
                 try:
-                    tmpfile = os.path.join(tmpdir, support.TESTFN)
+                    tmpfile = os.path.join(tmpdir, os_helper.TESTFN)
                     handles.append(os.open(tmpfile, os.O_WRONLY|os.O_CREAT))
                 except OSError as e:
                     if e.errno != errno.EMFILE:
@@ -2881,7 +2884,7 @@
     def test_select_unbuffered(self):
         # Issue #11459: bufsize=0 should really set the pipes as
         # unbuffered (and therefore let select() work properly).
-        select = support.import_module("select")
+        select = import_helper.import_module("select")
         p = subprocess.Popen([sys.executable, "-c",
                               'import sys;'
                               'sys.stdout.write("apple")'],
@@ -2909,7 +2912,7 @@
         self.addCleanup(p.stderr.close)
         ident = id(p)
         pid = p.pid
-        with support.check_warnings(('', ResourceWarning)):
+        with warnings_helper.check_warnings(('', ResourceWarning)):
             p = None
 
         if mswindows:
@@ -2934,7 +2937,7 @@
         self.addCleanup(p.stderr.close)
         ident = id(p)
         pid = p.pid
-        with support.check_warnings(('', ResourceWarning)):
+        with warnings_helper.check_warnings(('', ResourceWarning)):
             p = None
 
         os.kill(pid, signal.SIGKILL)
@@ -3288,7 +3291,8 @@
         self.assertIn(b"OSError", stderr)
 
         # Check for a warning due to using handle_list and close_fds=False
-        with support.check_warnings((".*overriding close_fds", RuntimeWarning)):
+        with warnings_helper.check_warnings((".*overriding close_fds",
+                                             RuntimeWarning)):
             startupinfo = subprocess.STARTUPINFO()
             startupinfo.lpAttributeList = {"handle_list": handles[:]}
             p = subprocess.Popen([sys.executable, "-c",