The summary says all, I got some problems with dnf configuration --scrub doesn't fix it , I needed do : rm -rf /home/var/cache/mock/fedora-21-x86_64/dnf_cache/ to fix my problem. Thanks.
This bug appears to have been reported against 'rawhide' during the Fedora 23 development cycle. Changing version to '23'. (As we did not run this process for some time, it could affect also pre-Fedora 23 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 23 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora23
--scrub=yum-cache deletes also DNF cache. However I admit it is not stated in man page. I will create alias and document it in man page.
Fixed in commit: * 72eb206 (origin/devel) provide --scrub=dnf-cache as alias for yum-cache [RHBZ#1241296]
mock-1.2.13-2.fc22 has been submitted as an update to Fedora 22. https://bodhi.fedoraproject.org/updates/FEDORA-2015-16053
mock-1.2.13-2.fc23 has been submitted as an update to Fedora 23. https://bodhi.fedoraproject.org/updates/FEDORA-2015-16054
mock-1.2.13-2.fc21 has been submitted as an update to Fedora 21. https://bodhi.fedoraproject.org/updates/FEDORA-2015-16056
mock-1.2.13-2.el7 has been submitted as an update to Fedora EPEL 7. https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2015-8114
mock-1.2.13-2.el6 has been submitted as an update to Fedora EPEL 6. https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2015-8115
mock-1.2.13-2.fc23 has been pushed to the Fedora 23 testing repository. If problems still persist, please make note of it in this bug report.\nIf you want to test the update, you can install it with \n su -c 'yum --enablerepo=updates-testing update mock'. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2015-16054
mock-1.2.13-2.fc21 has been pushed to the Fedora 21 testing repository. If problems still persist, please make note of it in this bug report.\nIf you want to test the update, you can install it with \n su -c 'yum --enablerepo=updates-testing update mock'. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2015-16056
mock-1.2.13-2.fc22 has been pushed to the Fedora 22 testing repository. If problems still persist, please make note of it in this bug report.\nIf you want to test the update, you can install it with \n su -c 'yum --enablerepo=updates-testing update mock'. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2015-16053
mock-1.2.13-2.el6 has been pushed to the Fedora EPEL 6 testing repository. If problems still persist, please make note of it in this bug report.\nIf you want to test the update, you can install it with \n su -c 'yum --enablerepo=updates-testing update mock'. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2015-8115
mock-1.2.13-2.el7 has been pushed to the Fedora EPEL 7 testing repository. If problems still persist, please make note of it in this bug report.\nIf you want to test the update, you can install it with \n su -c 'yum --enablerepo=updates-testing update mock'. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2015-8114
mock-1.2.13-2.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
mock-1.2.13-2.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
mock-1.2.13-2.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.
mock-1.2.13-2.el7 has been pushed to the Fedora EPEL 7 stable repository. If problems still persist, please make note of it in this bug report.
mock-1.2.13-2.el6 has been pushed to the Fedora EPEL 6 stable repository. If problems still persist, please make note of it in this bug report.