Permission denied by op

[Randy Bush]

i am invoking op from a python proggy which does an op.system() of

   op chmod 640 /usr/local/etc/tac_plus.conf

i get "Permission denied by op" 

% ls -l /usr/local/etc/op.access
-r--------  1 root  wheel  149 Jan 13 07:41 /usr/local/etc/op.access

% cat /usr/local/etc/op.access
# 2007.01.13
#
#DEFAULT users=src
#
chown   /usr/sbin/chown $* ; users=src
chmod   /bin/chmod $* ; users=src
rsync   /usr/local/bin/rsync $* ; users=src
#

% id
uid=1007(src) gid=1006(srctree) groups=1006(srctree)

clue bat, please

randy