Quote from http://docs.python.org/3.0/c-api/arg.html, regarding the "s"
argument:

"""
s (string or Unicode object) [const char *]

    Convert a Python string or Unicode object to a C pointer to a
character string. You must not provide storage for the string itself; a
pointer to an existing string is stored into the character pointer
variable whose address you pass. 
"""

I guess the phrase "you must not provide storage" is a failed
translation and not meant like that. It should say "you are not required
to provide storage". It's confusing to have such strong wording without
reason.