/usr/share/tuxpaint/fonts/FreeSerifItalic.ttf is in tuxpaint-data 1:0.9.21-1.1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/tuxpaint/fonts/../../fonts/truetype/freefont/FreeSerifItalic.ttf