add content to the env script.

def add_to_env(self, content):
        """
        add content to the env script.
        """
        if not self.rewrite_config:
            raise DirectoryException("Error! Directory was not intialized w/ rewrite_config.")
        if not self.env_file:
            self.env_path, self.env_file = self.__get_env_handle(self.root_dir)
        self.env_file.write(content + '\n')