It seems like I can't set the content of a PrivFile to arbitrary bytes.

$ propellor --set 'PrivFile "mysecret.key"' 'mycontext' < ~/mysecret.key
find . | grep -v /.git/ | grep -v /tmp/ | grep -v /dist/ | grep -v /doc/ | egrep '\.hs$' | xargs hothasktags | perl -ne 'print; s/Propellor\.Property\.//; print' | sort > tags  2>/dev/null || true
cabal build
Building propellor-2.2.1...
Preprocessing library propellor-2.2.1...
In-place registering propellor-2.2.1...
Preprocessing executable 'propellor' for propellor-2.2.1...
Preprocessing executable 'propellor-config' for propellor-2.2.1...
[70 of 70] Compiling Main             ( src/config.hs, dist/build/propellor-config/propellor-config-tmp/Main.o )
Linking dist/build/propellor-config/propellor-config ...
ln -sf dist/build/propellor-config/propellor-config propellor


Enter private data on stdin; ctrl-D when done:
propellor: <stdin>: hGetContents: invalid argument (invalid byte sequence)

done! --Joey