* Better handling of empty/invalid passwords
empty password files are global error and cause an
exit. A warning is also emitted with more detail.
ie, if any of the password/secret sources provide
a bogus password (ie, empty) or fail (exception,
ctrl-d, EOFError), we stop at the first error and exit.
This makes behavior when entering empty password at
prompt match 2.3 (ie, an error)
