Help with using local copy of leap seconds file

Hi. Sorry to be asking a simple question. I am working behind a firewall and need to use a local copy of a leap seconds file. I read documentation and tried this, after clearing the cache.

from astropy.utils import iers
iers.conf.auto_download = False
where IERS_Leap_Second.dat is a local copy that I can update myself. This seemed to work, but I tested by changing the leap second values in the local file. This did not change the conversion from UTC to TAI. Astropy is still using some built-in table of correct leap second values. How can I get Astropy to use my input values? Thank you.