Control: reopen -1 looking at the build log at https://buildd.debian.org/status/fetch.php?pkg=calibre&arch=amd64&ver=5.5.0%2Bdfsg-2&stamp=1606054693&raw=0
[...] find debian/tmp -type f | xargs sed -i '1 { /^#!.*python/ s_^.*$_#!/usr/bin/python3.9_ }' why? [...] make[1]: Leaving directory '/<<PKGBUILDDIR>>' dh_python3 -a -O--buildsystem=makefile E: dh_python3 dh_python3:176: no package to act on (python3-foo or one with ${python3:Depends} in Depends) something goes wrong Depends: libc6 (>= 2.29), libespeak-ng1 (>= 1.50+dfsg), libfontconfig1 (>= 2.12.6), libfreetype6 (>= 2.6), libgcc-s1 (>= 3.0), libglib2.0-0 (>= 2.12.0), libhunspell-1.7-0, libhyphen0 (>= 2.8.7), libicu67 (>= 67.1-1~), libmtp9 (>= 1.1.5), libpodofo0.9.6 (>= 0.9.6+dfsg), libpython3.9 (>= 3.9.0~b4), libqt5core5a (>= 5.15.1), libqt5dbus5 (>= 5.12), libqt5gui5 (>= 5.14.1) | libqt5gui5-gles (>= 5.14.1), libqt5widgets5 (>= 5.12), libstdc++6 (>= 5.2), libusb-1.0-0 (>= 2:1.0.9), qtbase-abi-5-15-1, python3-pyqt5.sip, python3 no python3:Depends dependency generated, and the 'python3' dependency is not good enough the calibre-bin package needs to end up with a dependency: python3 (>= 3.9), python3 (<< 3.10)