The only use of mimetools inside cgi is in parse_multipart, which is 
untested and has huge warnings like these ones:

"""
XXX This does not parse nested multipart parts -- use FieldStorage for
that.

XXX This should really be subsumed by FieldStorage altogether -- no
point in having two implementations of the same parsing algorithm.
Also, FieldStorage protects itself better against certain DoS attacks
by limiting the size of the data read in one chunk.  The API here
does not support that kind of protection.  This also affects parse()
since it can call parse_multipart().
"""