In 3.8, holiday exceptions are still being ignored. What's happening is that when calculating the due date and skipping the days that the library is closed, the holiday exceptions are being ignored and skipped, even though the library is open. To reproduce: 1) Set a repeating holiday. Closed on Sats and Suns, for example. 2) Make an exception. We're open this Saturday (but closed all of the other ones). 3) Set usedaysmode sys pref to skip all days the library is closed. 4) Set renewalbaseperiod to use the current date. 5) Check out some items. See if due date is correctly calculated. 6) Renew some items. See if due date is correctly calculated.
Could someoene retest this on a newer version? 3.8 is EOL.
This appears to be fixed in master.