Per https://bugzilla.redhat.com/show_bug.cgi?id=1840780#c2 this happens on python >= 3.8.3. As Focal ships 3.8.5 we get this bug. Juanjo linked and attached the upstream patch already, which is included in Calibre >= 4.15. Focal ships Calibre version 4.99.4 which I assume is some pre-release version of the Calibre 5 series which didn't yet include this fix. Calibre 5 is now available and presumably would also fix this issue.
Per https:/ /bugzilla. redhat. com/show_ bug.cgi? id=1840780# c2 this happens on python >= 3.8.3. As Focal ships 3.8.5 we get this bug. Juanjo linked and attached the upstream patch already, which is included in Calibre >= 4.15. Focal ships Calibre version 4.99.4 which I assume is some pre-release version of the Calibre 5 series which didn't yet include this fix. Calibre 5 is now available and presumably would also fix this issue.