misc: remove code that was used by old theming (#71998)
remove theme keyword variants (#70129)
misc: remove custom error page code (#63773)
trivial: apply black
misc: import N_ instead of relying on builtin (#40373)
python3: replace has_key usage (#38094)
remove support for announces (#37967)
remove support for agenda/events (#37967)
misc: use relative imports (#36518)
force body to be a string (not <htmltext>)
adapt to template changes (#25057)
update origin of TextsDirectory import (#21627)
misc: change module name and installation directory (#17959)