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.
check_call() will raise CalledProcessError, if the called process returns a non-zero return code.