Why does handling multiple exceptions require a tuple, but not a list?

Consider the following example:

def main_list(error_type):

    try:
        if error_type == 'runtime':
            raise RuntimeError("list error")
        if error_type == 'valueerror':
            raise ValueError("list error")

    except [RuntimeError, ValueError] as e:
        print str(e)

def main_tuple(error_type):

    try:
        if error_type == 'runtime':
            raise RuntimeError("tuple error")
        if error_type == 'valueerror':
            raise ValueError("tuple error")

    except (RuntimeError, ValueError) as e:
        print str(e)


main_tuple('runtime')
main_tuple('valueerror')

main_list('runtime')
main_list('valueerror')

The tuple is the correct way to handle multiple exception types. Using a list for the multiple exception types causes neither to be handled.

I am wondering why Python syntax requires a tuple for multiple exception types. The docs say that it uses a tuple, so perhaps it is just "never was implemented using a list instead of a tuple."

It seems reasonable to me that a list could also be used in this situation, conceptually at least.

Is there any reason why Python uses a tuple instead of a list for this situation?