SF bug #887946, segfault if redirecting directory

Also provide a warning if a directory is passed on the command line.
Add minimal command line test.

Will backport.

Lib/test/test_cmd_line.py

@@ -0,0 +1,50 @@
+
+import test.test_support, unittest
+import sys
+import popen2
+
+class CmdLineTest(unittest.TestCase):
+    def start_python(self, cmd_line):
+        outfp, infp = popen2.popen4('%s %s' % (sys.executable, cmd_line))
+        infp.close()
+        data = outfp.read()
+        outfp.close()
+        return data
+
+    def test_directories(self):
+        self.assertTrue('is a directory' in self.start_python('.'))
+        self.assertTrue('is a directory' in self.start_python('< .'))
+
+    def verify_valid_flag(self, cmd_line):
+        data = self.start_python(cmd_line)
+        self.assertTrue(data.endswith('\n'))
+        self.assertTrue('Traceback' not in data)
+
+    def test_environment(self):
+        self.verify_valid_flag('-E')
+
+    def test_optimize(self):
+        self.verify_valid_flag('-O')
+        self.verify_valid_flag('-OO')
+
+    def test_q(self):
+        self.verify_valid_flag('-Qold')
+        self.verify_valid_flag('-Qnew')
+        self.verify_valid_flag('-Qwarn')
+        self.verify_valid_flag('-Qwarnall')
+
+    def test_site_flag(self):
+        self.verify_valid_flag('-S')
+
+    def test_usage(self):
+        self.assertTrue('usage' in self.start_python('-h'))
+
+    def test_version(self):
+        version = 'Python %d.%d' % sys.version_info[:2]
+        self.assertTrue(self.start_python('-V').startswith(version))
+
+def test_main():
+    test.test_support.run_unittest(CmdLineTest)
+
+if __name__ == "__main__":
+    test_main()