Issue #17835: Fix test_io when the default OS pipe buffer size is larger than one million bytes.
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 5cd28f5..63a0508 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2880,7 +2880,7 @@
             # The buffered IO layer must check for pending signal
             # handlers, which in this case will invoke alarm_interrupt().
             self.assertRaises(ZeroDivisionError,
-                              wio.write, item * (3 * 1000 * 1000))
+                        wio.write, item * (support.PIPE_MAX_SIZE // len(item) + 1))
             t.join()
             # We got one byte, get another one and check that it isn't a
             # repeat of the first one.
@@ -2978,7 +2978,7 @@
         select = support.import_module("select")
         # A quantity that exceeds the buffer size of an anonymous pipe's
         # write end.
-        N = 1024 * 1024
+        N = support.PIPE_MAX_SIZE
         r, w = os.pipe()
         fdopen_kwargs["closefd"] = False
         # We need a separate thread to read from the pipe and allow the