The on/off pulse shifted the whole line by one character during the
dark frames (off-frame printed one space fewer than the block frame).
Per YuKu: keep the block ALWAYS present and alternate its colour
instead — blue (44) <-> dark grey (100, bright black). Layout is
constant, pulse is colour-based, nothing moves but the block itself.
Also: disable_selinux now mkdir -p's /etc/selinux before writing a
fresh config (harness caught a die on a missing parent dir).
Pathfinder
4a53155c7e