I've upgraded 4.2 to 4.3 apparently successfully. Only issue noted:
Can't exec "/tmp/weewx.config.csy0Mc": Permission denied at /usr/share/perl/5.30/IPC/Open3.pm line 281.
open2: exec of /tmp/weewx.config.csy0Mc configure 4.2.0-1 failed: Permission denied at /usr/share/perl5/Debconf/ConfModule.pm line 59.
(Reading database ... 106466 files and directories currently installed.)
Significant? I've compared the weewx.conf files before and after and all seems well.