Comparision of two rpms with html-dir set hangs diffoscope

Yocto Project runs diffoscope in our CI to help us debug reproducibility issues. We've tried to enable this for our rpms (currently its running against ipk+deb) but when binaries differ, it hangs. We're calling diffoscope with --html-dir, if we remove that it doesn't hang but the output is less useful to us. Example binaries that hang it are comparing https://autobuilder.yocto.io/pub/repro-fail/oe-reproducible-20210224-vy8equte/packages/reproducibleA/tmp/deploy/rpm/noarch/cantarell-fonts-0.301-r0.noarch.rpm with https://autobuilder.yocto.io/pub/repro-fail/oe-reproducible-20210224-vy8equte/packages/reproducibleB/tmp/deploy/rpm/noarch/cantarell-fonts-0.301-r0.noarch.rpm We've confirmed seeing this with 166 and 167.