cowbuilder --update W: --override-config is not set; not updating apt.conf Read the manpage for details

The following is my ~/.pbuilderrc $ cat .pbuilderrc BASEPATH="/var/cache/pbuilder/sid-amd64/base.cow" DISTRIBUTION="sid" MIRRORSITE="http://deb.debian.org/debian/ " # Enable build log PKGNAME_LOGFILE="yes" whenever I run sudo cowbuilder --update I get the following warning - $ sudo cowbuilder --update I: Copying COW directory I: forking: rm -rf /var/cache/pbuilder/build/cow.8567 I: forking: cp -al /var/cache/pbuilder/sid-amd64/base.cow /var/cache/pbuilder/build/cow.8567 I: unlink for ilistfile /var/cache/pbuilder/build/cow.8567/.ilist failed, it didn't exist? I: Invoking pbuilder I: forking: pbuilder update --buildplace /var/cache/pbuilder/build/cow.8567 --mirror http://deb.debian.org/debian/ --distribution sid --no-targz --internal-chrootexec 'chroot /var/cache/pbuilder/build/cow.8567 cow-shell' I: Running in no-targz mode I: Current time: Fri Aug 31 23:18:47 IST 2018 I: pbuilder-time-stamp: 1535737727 I: copying local configuration W: --override-config is not set; not updating apt.conf Read the manpage for details. Can somebody tell me what --override-config is all about and where it needs to be set and how ?