capybara/virtualenv/lib/python2.7/site-packages/setuptools/sandbox.py
def run_setup(setup_script, args):
    """Run a distutils setup script, sandboxed in its directory"""
    setup_dir = os.path.abspath(os.path.dirname(setup_script))
    with setup_context(setup_dir):
        try:
            sys.argv[:] = [setup_script]+list(args)
            sys.path.insert(0, setup_dir)
            # reset to include setup dir, w/clean callback list
            working_set.__init__()
            working_set.callbacks.append(lambda dist:dist.activate())
            def runner():
                ns = dict(__file__=setup_script, __name__='__main__')
                _execfile(setup_script, ns)
            DirectorySandbox(setup_dir).run(runner)
        except SystemExit as v:
            if v.args and v.args[0]:
                raise
def run_setup(setup_script, args):
    """Run a distutils setup script, sandboxed in its directory"""
    setup_dir = os.path.abspath(os.path.dirname(setup_script))
    with setup_context(setup_dir):
        try:
            sys.argv[:] = [setup_script]+list(args)
            sys.path.insert(0, setup_dir)
            # reset to include setup dir, w/clean callback list
            working_set.__init__()
            working_set.callbacks.append(lambda dist:dist.activate())
            def runner():
                ns = dict(__file__=setup_script, __name__='__main__')
                _execfile(setup_script, ns)
            DirectorySandbox(setup_dir).run(runner)
        except SystemExit as v:
            if v.args and v.args[0]:
                raise
Run a distutils setup script, sandboxed in its directory