bpo-40275: Use new test.support helper submodules in tests (GH-21314)

diff --git a/Lib/test/test_httplib.py b/Lib/test/test_httplib.py
index e909980..1ac31bf 100644
--- a/Lib/test/test_httplib.py
+++ b/Lib/test/test_httplib.py
@@ -13,7 +13,10 @@
 TestCase = unittest.TestCase
 
 from test import support
+from test.support import os_helper
 from test.support import socket_helper
+from test.support import warnings_helper
+
 
 here = os.path.dirname(__file__)
 # Self-signed cert file for 'localhost'
@@ -1766,14 +1769,14 @@
         with self.assertRaises(ssl.CertificateError):
             h.request('GET', '/')
         # Same with explicit check_hostname=True
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             h = client.HTTPSConnection('localhost', server.port,
                                        context=context, check_hostname=True)
         with self.assertRaises(ssl.CertificateError):
             h.request('GET', '/')
         # With check_hostname=False, the mismatching is ignored
         context.check_hostname = False
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             h = client.HTTPSConnection('localhost', server.port,
                                        context=context, check_hostname=False)
         h.request('GET', '/nonexistent')
@@ -1792,7 +1795,7 @@
         h.close()
         # Passing check_hostname to HTTPSConnection should override the
         # context's setting.
-        with support.check_warnings(('', DeprecationWarning)):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
             h = client.HTTPSConnection('localhost', server.port,
                                        context=context, check_hostname=True)
         with self.assertRaises(ssl.CertificateError):
@@ -1908,10 +1911,10 @@
         self.assertEqual(b'body\xc1', f.read())
 
     def test_text_file_body(self):
-        self.addCleanup(support.unlink, support.TESTFN)
-        with open(support.TESTFN, "w") as f:
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        with open(os_helper.TESTFN, "w") as f:
             f.write("body")
-        with open(support.TESTFN) as f:
+        with open(os_helper.TESTFN) as f:
             self.conn.request("PUT", "/url", f)
             message, f = self.get_headers_and_fp()
             self.assertEqual("text/plain", message.get_content_type())
@@ -1923,10 +1926,10 @@
             self.assertEqual(b'4\r\nbody\r\n0\r\n\r\n', f.read())
 
     def test_binary_file_body(self):
-        self.addCleanup(support.unlink, support.TESTFN)
-        with open(support.TESTFN, "wb") as f:
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        with open(os_helper.TESTFN, "wb") as f:
             f.write(b"body\xc1")
-        with open(support.TESTFN, "rb") as f:
+        with open(os_helper.TESTFN, "rb") as f:
             self.conn.request("PUT", "/url", f)
             message, f = self.get_headers_and_fp()
             self.assertEqual("text/plain", message.get_content_type())