Issue #443: post-commit hook script (error) output lost
            Fixing portability issue in the test.

* subversion/tests/clients/cmdline/commit_tests.py
(post_commit_hook_test): Modified to make the post-commit hook use
the create_python_hook_script function to make it portable to
windows and unix systems.

* subversion/tests/clients/cmdline/svntest/main.py
(create_python_hook_script): New function to create a python based hook
script portable to windows and unix operating systems.