bpo-46648: Rewrite test_urllib2.test_issue16464() with a local HTTP server (GH-31186)

Re-enable test_issue16464() of test_urllib2, move it to urllib2_localnet
and use the local HTTP server rather than an external HTTP server.

Lib/test/test_urllib2.py

@@ -1788,24 +1788,6 @@ class MiscTests(unittest.TestCase):
         self.opener_has_handler(o, MyHTTPHandler)
         self.opener_has_handler(o, MyOtherHTTPHandler)
 
-    @unittest.skipUnless(support.is_resource_enabled('network'),
-                         'test requires network access')
-    # bpo-46648: test fails randomly with "http://www.example.com/" URL
-    @unittest.skipIf(True, "POST request to http://www.example.com/ fail randomly")
-    def test_issue16464(self):
-        with socket_helper.transient_internet("http://www.example.com/"):
-            opener = urllib.request.build_opener()
-            request = urllib.request.Request("http://www.example.com/")
-            self.assertEqual(None, request.data)
-
-            opener.open(request, "1".encode("us-ascii"))
-            self.assertEqual(b"1", request.data)
-            self.assertEqual("1", request.get_header("Content-length"))
-
-            opener.open(request, "1234567890".encode("us-ascii"))
-            self.assertEqual(b"1234567890", request.data)
-            self.assertEqual("10", request.get_header("Content-length"))
-
     def test_HTTPError_interface(self):
         """
         Issue 13211 reveals that HTTPError didn't implement the URLError

Lib/test/test_urllib2_localnet.py

@@ -660,6 +660,24 @@ class TestUrlopen(unittest.TestCase):
                              (index, len(lines[index]), len(line)))
         self.assertEqual(index + 1, len(lines))
 
+    def test_issue16464(self):
+        # See https://bugs.python.org/issue16464
+        # and https://bugs.python.org/issue46648
+        handler = self.start_server([
+            (200, [], b'any'),
+            (200, [], b'any'),
+        ])
+        opener = urllib.request.build_opener()
+        request = urllib.request.Request("http://localhost:%s" % handler.port)
+        self.assertEqual(None, request.data)
+
+        opener.open(request, "1".encode("us-ascii"))
+        self.assertEqual(b"1", request.data)
+        self.assertEqual("1", request.get_header("Content-length"))
+
+        opener.open(request, "1234567890".encode("us-ascii"))
+        self.assertEqual(b"1234567890", request.data)
+        self.assertEqual("10", request.get_header("Content-length"))
 
 def setUpModule():
     thread_info = threading_helper.threading_setup()