don't use subprocess.call with PIPEs as the child can fill the pipe buf and

deadlock. add a warning to subprocess docs about this, similar to Popen.wait's.
refs http://bugs.jython.org/issue1351

Doc/library/subprocess.rst

@@ -157,6 +157,12 @@ This module also defines two shortcut functions:
 
       retcode = call(["ls", "-l"])
 
+   .. warning::
+
+      Like :meth:`Popen.wait`, this will deadlock if the child process
+      generates enough output to a stdout or stderr pipe such that it blocks
+      waiting for the OS pipe buffer to accept more data.
+
 
 .. function:: check_call(*popenargs, **kwargs)
 
@@ -171,6 +177,10 @@ This module also defines two shortcut functions:
 
    .. versionadded:: 2.5
 
+   .. warning::
+
+      See the warning for :func:`call`.
+
 
 .. function:: check_output(*popenargs, **kwargs)
 

Lib/test/test_cmd_line.py

@@ -2,6 +2,7 @@
 # All tests are executed with environment variables ignored
 # See test_cmd_line_script.py for testing of script execution
 
+import os
 import test.test_support, unittest
 import sys
 import subprocess
@@ -29,8 +30,9 @@ class CmdLineTest(unittest.TestCase):
     def exit_code(self, *args):
         cmd_line = [sys.executable, '-E']
         cmd_line.extend(args)
-        return subprocess.call(cmd_line, stdout=subprocess.PIPE,
-                                         stderr=subprocess.PIPE)
+        with open(os.devnull, 'w') as devnull:
+            return subprocess.call(cmd_line, stdout=devnull,
+                                   stderr=subprocess.STDOUT)
 
     def test_directories(self):
         self.assertNotEqual(self.exit_code('.'), 0)