The changelog is not available in mintupdate

[saber716rus]

Describe the bug
I found that the changelog of packages is not shown

Screenshots
If applicable, add screenshots to help explain your problem, you can just drag & drop them here.

To Reproduce
Steps to reproduce the behavior:

1. click on the "Change Log" tab
2. I see that the window says "The changelog is unavailable"

Expected behavior
I would like to see changelog package updates

Distribution:

• Linux Mint
• [*] LMDE
• Other (please specify)

Software version:
See Help > About in Update Manager.

Logs:
Copy & paste the log output from Update Manager > View > Information here.
6.0.9
Crash report:
saber716rus@BOM-WXX9 ~> mintupdate
saber716rus@BOM-WXX9 ~> /usr/lib/linuxmint/mintUpdate/mintUpdate.py:1379: DeprecationWarning: Gdk.threads_init is deprecated
Gdk.threads_init()
/usr/lib/linuxmint/mintUpdate/mintUpdate.py:1764: DeprecationWarning: Gdk.threads_enter is deprecated
Gdk.threads_enter()
/usr/lib/linuxmint/mintUpdate/mintUpdate.py:803: DeprecationWarning: Gdk.threads_leave is deprecated
Gdk.threads_leave()
Flatpak: done generating updates
Trying to fetch the changelog from: https://metadata.ftp-master.debian.org/changelogs/main/b/bind9/bind9_9.18.24-1_changelog
Trying to fetch the changelog from: https://metadata.ftp-master.debian.org/changelogs/contrib/b/bind9/bind9_9.18.24-1_changelog
Trying to fetch the changelog from: https://metadata.ftp-master.debian.org/changelogs/non-free/b/bind9/bind9_9.18.24-1_changelog

Additional context
Add any other context about the problem you think might be relevant.

Locale:
If the problem is with text not getting displayed correctly, paste the output of the terminal command locale.
saber716rus@BOM-WXX9 ~> locale
LANG=ru_RU.UTF-8
LANGUAGE=
LC_CTYPE="ru_RU.UTF-8"
LC_NUMERIC="ru_RU.UTF-8"
LC_TIME="ru_RU.UTF-8"
LC_COLLATE="ru_RU.UTF-8"
LC_MONETARY="ru_RU.UTF-8"
LC_MESSAGES="ru_RU.UTF-8"
LC_PAPER="ru_RU.UTF-8"
LC_NAME="ru_RU.UTF-8"
LC_ADDRESS="ru_RU.UTF-8"
LC_TELEPHONE="ru_RU.UTF-8"
LC_MEASUREMENT="ru_RU.UTF-8"
LC_IDENTIFICATION="ru_RU.UTF-8"
LC_ALL=
saber716rus@BOM-WXX9 ~>

[kneekoo]

Related: #767