Execute finder script within the temporary venv context.

def execute_finder(self, manager, package_name):
        """ Execute finder script within the temporary venv context. """
        filename = '{env_path}/results.json'.format(env_path=manager.env_path)
        subprocess.call([
            manager.venv_python, self._finder_path, package_name, filename
        ])

        # Load results into this context
        json_str = open(filename, 'r').read()
        return json.loads(json_str)