issue7213 + issue2320: Cause a DeprecationWarning if the close_fds argument is

not passed to subprocess.Popen as the default value will be changing in a
future Python to the safer and more often desired value of True.

DeprecationWarnings that show up in a lot of existing code are controversial
and have caused pain in the past.  I'd like to leave this on for 3.2 beta1 and
see how things go.  We can remove the warning if it is deemed too noisy during
any betas.  (case study: the md5 and sha module DeprecationWarnings are loathed
around the world as those modules were never going to be removed in 2.x and
2to3 has a fixer for code that uses them)

Lib/test/test_subprocess.py

@@ -9,6 +9,7 @@ import tempfile
 import time
 import re
 import sysconfig
+import warnings
 try:
     import gc
 except ImportError:
@@ -57,6 +58,34 @@ class BaseTestCase(unittest.TestCase):
         self.assertEqual(actual, expected, msg)
 
 
+class DeprecationWarningTests(BaseTestCase):
+    def setUp(self):
+        BaseTestCase.setUp(self)
+        self._saved_warn = warnings.warn
+        self._warn_calls = []
+        warnings.warn = self._record_warn
+
+    def tearDown(self):
+        warnings.warn = self._saved_warn
+        BaseTestCase.tearDown(self)
+
+    def _record_warn(self, *args):
+        """A warnings.warn function that records calls."""
+        self._warn_calls.append(args)
+        self._saved_warn(*args)
+
+    def testCloseFdsWarning(self):
+        quick_process = [sys.executable, "-c", "import sys; sys.exit(0)"]
+        subprocess.call(quick_process, close_fds=True)
+        self.assertEqual([], self._warn_calls)
+        subprocess.call(quick_process, close_fds=False)
+        self.assertEqual([], self._warn_calls)
+        self.assertWarns(DeprecationWarning, subprocess.call, quick_process)
+        self.assertEqual(1, len(self._warn_calls))
+        self.assertIn('close_fds parameter was not specified',
+                      self._warn_calls[0][0])
+
+
 class ProcessTestCase(BaseTestCase):
 
     def test_call_seq(self):
@@ -1233,7 +1262,8 @@ def test_main():
                   ProcessTestCaseNoPoll,
                   HelperFunctionTests,
                   CommandsWithSpaces,
-                  ContextManagerTests)
+                  ContextManagerTests,
+                  DeprecationWarningTests)
 
     support.run_unittest(*unit_tests)
     support.reap_children()