differences between ubuntu and fedora python

[Eric S. Johansson]

fedora
[root at lbox ~]# file /etc/postfix/transport*
/etc/postfix/transport:        ASCII English text
/etc/postfix/transport.db:     Berkeley DB (Hash, version 8, native 
byte-order)


# python /usr/lib/python2.4/whichdb.py /etc/postfix/transport
UNKNOWN /etc/postfix/transport
# python /usr/lib/python2.4/whichdb.py /etc/postfix/transport.db
dbhash /etc/postfix/transport.db

ubuntu
/etc/postfix/transport:    ASCII text
/etc/postfix/transport.db: Berkeley DB (Hash, version 8, native byte-order)

# python /usr/lib/python2.4/whichdb.py /etc/postfix/transport
dbm /etc/postfix/transport
# python /usr/lib/python2.4/whichdb.py /etc/postfix/transport.db
dbhash /etc/postfix/transport.db

why the difference?  according to the whichdb code, It looks for the .db 
form and should pick it up except it isn't.