### 6.8.1.2 Exceptions

Exceptions raised in the child process, before the new program has started to execute, will be re-raised in the parent. Additionally, the exception object will have one extra attribute called `child_traceback`, which is a string containing traceback information from the childs point of view.

The most common exception raised is `OSError`. This occurs, for example, when trying to execute a non-existent file. Applications should prepare for `OSError` exceptions.

A `ValueError` will be raised if `Popen` is called with invalid arguments.