This bug only appears to be a cosmetic one where the TZ offset
would be calculated on current_year/01/01 so would remain in
daylight saving offset when displaying the timezones list.
(Note by amotoki)
The minimum version of Babel is bumped to 2.6.0
as Babel 2.3.4 returns "New Zealand Time" instead of "New Zealand
(Auckland) Time" returned from the latest Babel (2.9.0).
It is not a good idea to handle such difference in Babel in our UT
and there is no reason to stick to Bump 2.3.4.
2.6.0 was chosen as it is available in Ubuntu Focal and there is
no more reason than this.