The gpg-agent could not start if the /root is mounted by docker when
the external path is long enough, a workaround is to use a different
GNUPGHOME for gpg key generation, and copy generated files to
/root/.gnupg afterwards
bonus: thanks to expect, we can a automated login process, if both
PROTONMAIL_USERNAME and PROTONMAIL_PASSWORD are set
Signed-off-by: Jeffrey Stoke <me@arhat.dev>