/lib/partman/choose_partition/ is in ubiquity 2.18.7.
This file is owned by root:root, with mode 0o755.
..
/lib/partman/choose_partition/20auto/
/lib/partman/choose_partition/20auto/choices
/lib/partman/choose_partition/20auto/do_option
/lib/partman/choose_partition/30lvm/
/lib/partman/choose_partition/30lvm/choices
/lib/partman/choose_partition/30lvm/do_option
/lib/partman/choose_partition/35crypto/
/lib/partman/choose_partition/35crypto/choices
/lib/partman/choose_partition/35crypto/do_option
/lib/partman/choose_partition/55divider_up/
/lib/partman/choose_partition/55divider_up/choices
/lib/partman/choose_partition/55divider_up/do_option
/lib/partman/choose_partition/60partition_tree/
/lib/partman/choose_partition/60partition_tree/choices
/lib/partman/choose_partition/60partition_tree/do_option
/lib/partman/choose_partition/65divider_down/
/lib/partman/choose_partition/65divider_down/choices
/lib/partman/choose_partition/65divider_down/do_option
/lib/partman/choose_partition/80undo/
/lib/partman/choose_partition/80undo/choices
/lib/partman/choose_partition/80undo/do_option
/lib/partman/choose_partition/90finish/
/lib/partman/choose_partition/90finish/choices
/lib/partman/choose_partition/90finish/do_option
/lib/partman/choose_partition/priority
/lib/partman/choose_partition/question