Bug#732819: fontconfig-config: Upgrading from 2.9.0-7 doesn't change /etc/fonts/fonts.conf which leads to misconfiguration

Some time after changing /etc/fonts/fonts.conf the problem completely returned, without any actions from me. Later I realized /etc/fonts/fonts.conf is not the one to blame here, so I can't understand why that edit to it happened to fix the problem temporarily. Today I found the true reason of

Bug#732819: fontconfig-config: Upgrading from 2.9.0-7 doesn't change /etc/fonts/fonts.conf which leads to misconfiguration

Package: fontconfig-config Version: 2.10.2-2 Severity: serious Justification: 3 Upgrading from 2.9.0-7 to 2.10 or 2.11 doesn't prompts to change /etc/fonts/fonts.conf and doesn't point to possible problem with keeping old fonts.conf version, although comment in the file says IT WILL BE REPLACED