Merge pull request gitpython-developers#447 from Xender/patch-1

Use proper syntax for conditional expressions.

Author: Byron

git/cmd.py

@@ -609,7 +609,7 @@ def execute(self, command,
                          bufsize=-1,
                          stdin=istream,
                          stderr=PIPE,
-                         stdout=with_stdout and PIPE or open(os.devnull, 'wb'),
+                         stdout=PIPE if with_stdout else open(os.devnull, 'wb'),
                          shell=self.USE_SHELL,
                          close_fds=(os.name == 'posix'),  # unsupported on windows
                          universal_newlines=universal_newlines,