sudo perl -pi -e 's,GRUB_CMDLINE_LINUX="(.*)"$,GRUB_CMDLINE_LINUX="$1 apparmor=1 security=apparmor",' /etc/default/grub

$ sudo update-grub

Fontconfig error: Cannot load default config file

(firefox:3875): Pango-WARNING **: failed to choose a font, expect ugly output. engine-type='PangoRenderFc', script='common'
Crash Annotation GraphicsCriticalError: |[0][GFX1]: no fonts - init: 1 fonts: 0 loader: 0 (t=0.206719) [GFX1]: no fonts - init: 1 fonts: 0 loader: 0
[3875] ###!!! ABORT: unable to find a usable font (Sans): file /tmp/buildd/firefox-47.0.1/gfx/thebes/gfxTextRun.cpp, line 1875
[3875] ###!!! ABORT: unable to find a usable font (Sans): file /tmp/buildd/firefox-47.0.1/gfx/thebes/gfxTextRun.cpp, line 1875
Segmentation fault