diff -r 7b0fd592cd08 Lib/subprocess.py
--- a/Lib/subprocess.py	Tue Apr 12 22:38:22 2016 +0200
+++ b/Lib/subprocess.py	Wed Apr 13 00:41:49 2016 +0200
@@ -1005,6 +1005,9 @@ class Popen(object):
         if not self._child_created:
             # We didn't get to successfully create a child process.
             return
+        if self.returncode is None:
+            warnings.warn("running subprocess %r" % self, ResourceWarning,
+                          source=self)
         # In case the child hasn't been waited on, check if it's done.
         self._internal_poll(_deadstate=_maxsize)
         if self.returncode is None and _active is not None:
@@ -1519,10 +1522,14 @@ class Popen(object):
                 os.close(errpipe_read)
 
             if errpipe_data:
+                self.returncode = 255
                 try:
-                    os.waitpid(self.pid, 0)
+                    pid, sts = os.waitpid(self.pid, 0)
+                    if pid == self.pid:
+                        self._handle_exitstatus(sts)
                 except ChildProcessError:
                     pass
+
                 try:
                     exception_name, hex_errno, err_msg = (
                             errpipe_data.split(b':', 2))
diff -r 7b0fd592cd08 Lib/test/test_subprocess.py
--- a/Lib/test/test_subprocess.py	Tue Apr 12 22:38:22 2016 +0200
+++ b/Lib/test/test_subprocess.py	Wed Apr 13 00:41:49 2016 +0200
@@ -447,8 +447,8 @@ class ProcessTestCase(BaseTestCase):
         p = subprocess.Popen([sys.executable, "-c",
                           'import sys; sys.stdout.write("orange")'],
                          stdout=subprocess.PIPE)
-        self.addCleanup(p.stdout.close)
-        self.assertEqual(p.stdout.read(), b"orange")
+        with p:
+            self.assertEqual(p.stdout.read(), b"orange")
 
     def test_stdout_filedes(self):
         # stdout is set to open file descriptor
@@ -478,8 +478,8 @@ class ProcessTestCase(BaseTestCase):
         p = subprocess.Popen([sys.executable, "-c",
                           'import sys; sys.stderr.write("strawberry")'],
                          stderr=subprocess.PIPE)
-        self.addCleanup(p.stderr.close)
-        self.assertStderrEqual(p.stderr.read(), b"strawberry")
+        with p:
+            self.assertStderrEqual(p.stderr.read(), b"strawberry")
 
     def test_stderr_filedes(self):
         # stderr is set to open file descriptor
@@ -513,8 +513,8 @@ class ProcessTestCase(BaseTestCase):
                               'sys.stderr.write("orange")'],
                              stdout=subprocess.PIPE,
                              stderr=subprocess.STDOUT)
-        self.addCleanup(p.stdout.close)
-        self.assertStderrEqual(p.stdout.read(), b"appleorange")
+        with p:
+            self.assertStderrEqual(p.stdout.read(), b"appleorange")
 
     def test_stdout_stderr_file(self):
         # capture stdout and stderr to the same open file
@@ -772,18 +772,19 @@ class ProcessTestCase(BaseTestCase):
                              stdin=subprocess.PIPE,
                              stdout=subprocess.PIPE,
                              universal_newlines=1)
-        p.stdin.write("line1\n")
-        p.stdin.flush()
-        self.assertEqual(p.stdout.readline(), "line1\n")
-        p.stdin.write("line3\n")
-        p.stdin.close()
-        self.addCleanup(p.stdout.close)
-        self.assertEqual(p.stdout.readline(),
-                         "line2\n")
-        self.assertEqual(p.stdout.read(6),
-                         "line3\n")
-        self.assertEqual(p.stdout.read(),
-                         "line4\nline5\nline6\nline7\nline8")
+        with p:
+            p.stdin.write("line1\n")
+            p.stdin.flush()
+            self.assertEqual(p.stdout.readline(), "line1\n")
+            p.stdin.write("line3\n")
+            p.stdin.close()
+            self.addCleanup(p.stdout.close)
+            self.assertEqual(p.stdout.readline(),
+                             "line2\n")
+            self.assertEqual(p.stdout.read(6),
+                             "line3\n")
+            self.assertEqual(p.stdout.read(),
+                             "line4\nline5\nline6\nline7\nline8")
 
     def test_universal_newlines_communicate(self):
         # universal newlines through communicate()
@@ -1417,8 +1418,8 @@ class POSIXProcessTestCase(BaseTestCase)
                               'sys.stdout.write(os.getenv("FRUIT"))'],
                              stdout=subprocess.PIPE,
                              preexec_fn=lambda: os.putenv("FRUIT", "apple"))
-        self.addCleanup(p.stdout.close)
-        self.assertEqual(p.stdout.read(), b"apple")
+        with p:
+            self.assertEqual(p.stdout.read(), b"apple")
 
     def test_preexec_exception(self):
         def raise_it():
@@ -1566,8 +1567,8 @@ class POSIXProcessTestCase(BaseTestCase)
         p = subprocess.Popen(["echo $FRUIT"], shell=1,
                              stdout=subprocess.PIPE,
                              env=newenv)
-        self.addCleanup(p.stdout.close)
-        self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")
+        with p:
+            self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")
 
     def test_shell_string(self):
         # Run command through the shell (string)
@@ -1576,8 +1577,8 @@ class POSIXProcessTestCase(BaseTestCase)
         p = subprocess.Popen("echo $FRUIT", shell=1,
                              stdout=subprocess.PIPE,
                              env=newenv)
-        self.addCleanup(p.stdout.close)
-        self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")
+        with p:
+            self.assertEqual(p.stdout.read().strip(b" \t\r\n\f"), b"apple")
 
     def test_call_string(self):
         # call() function with string argument on UNIX
@@ -1609,8 +1610,8 @@ class POSIXProcessTestCase(BaseTestCase)
         for sh in shells:
             p = subprocess.Popen("echo $0", executable=sh, shell=True,
                                  stdout=subprocess.PIPE)
-            self.addCleanup(p.stdout.close)
-            self.assertEqual(p.stdout.read().strip(), bytes(sh, 'ascii'))
+            with p:
+                self.assertEqual(p.stdout.read().strip(), bytes(sh, 'ascii'))
 
     def _kill_process(self, method, *args):
         # Do not inherit file handles from the parent.
@@ -2268,7 +2269,9 @@ class POSIXProcessTestCase(BaseTestCase)
         self.addCleanup(p.stderr.close)
         ident = id(p)
         pid = p.pid
-        del p
+        with support.check_warnings(('', ResourceWarning)):
+            p = None
+
         # check that p is in the active processes list
         self.assertIn(ident, [id(o) for o in subprocess._active])
 
@@ -2287,7 +2290,9 @@ class POSIXProcessTestCase(BaseTestCase)
         self.addCleanup(p.stderr.close)
         ident = id(p)
         pid = p.pid
-        del p
+        with support.check_warnings(('', ResourceWarning)):
+            p = None
+
         os.kill(pid, signal.SIGKILL)
         # check that p is in the active processes list
         self.assertIn(ident, [id(o) for o in subprocess._active])