Upgrade to Weblate 3.x
Originally created by @intrigeri on #16943 (Redmine)
Wrt. the dependencies and their status in Debian, see tails#10038 (comment 73928).
Related issues
- Related to #16994 (closed)
- Related to tails#17050 (closed)
- Related to #16183 (closed)
- Blocks tails#16221 (closed)
- Blocks tails#16974
- Blocks #17358 (closed)