/usr/share/compass/frameworks/fancy-buttons/stylesheets/_fancy_buttons.sass is in compass-fancy-buttons-plugin 1.1.1~20120313-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | @warn "DEPRECATED: Please change your @import of fancy_buttons.sass to: @import \"fancy-buttons\""
@import fancy-buttons
|