PSA: workaround for segfault when running dnf update in F30

<tl;dr> librepo-1.9.6 has a major bug that will cause a segfault when a repository has zchunk metadata. To temporarily work around the problem, set zchunk=False in /etc/dnf/dnf.conf or wait until the next updates push comes out </tl;dr> About a week ago, we disabled zchunk metadata in the main F30 repository because of arm-specific compose problems[1]. The problems were fixed and we enabled zchunk metadata in F30 updates-testing yesterday, but, in the interval when there were no zchunk-enabled repositories, librepo-1.9.6 was released, and it has a major bug where it segfaults whenever dnf update is run on a repository with zchunk metadata. We've disabled zchunk metadata for F30 updates-testing and doing a new push now. I have submitted a fix[2] for the bug, but for now any F30 users need to do one of the following: * Wait until the next updates push is out. It won't have zchunk metadata, so updates will work normally again. * Set zchunk=False in /etc/dnf/dnf.conf. This will force dnf to fall back to non-zchunk metadata, bypassing the bug. Many apologies for the inconvenience. Jonathan [1] https://pagure.io/dusty/failed-composes/issue/1703 [2] https://github.com/rpm-software-management/librepo/pull/148