build: replace verstion extraction via set to use python The version of roundup was extracted from roundup/__init__.py by sed. It is used to label the roundup.pot template file. Replaced the sed setup by importing roundup and printing the __Version__ variable. This should be less fragile to spacing and other changes.

# human timezones
pytz
# indexer
Whoosh
# xapian is also installed
# extra database support
psycopg2
mysqlclient
redis
# encryption
gpg
# java web tokens
PyJWT
# extra HTTP compression methods
Brotli
zstd
# jinja2 template engine
Jinja2