Dear Maintainer,

When I run the following command:

    dget -du http://xxxxxx

I get the dget usage message, and the command exits with 0. It should
exit with non-zero instead, as it failed to do anything useful. The
exit 0 in this case makes it a little harder to use dget
programmatically, as for example in a CI system.

Complete output:

    liw@exolobe1$ dget -du http://xxxxxx
    Usage: dget [options] URL ...
           dget [options] [--all] package[=version] ...

    Downloads Debian packages (source and binary) from the specified URLs (first form),
    or using the mirror configured in /etc/apt/sources.list(.d) (second form).
    It is capable of downloading several packages at once.

       -a, --all       Package is a source package; download all binary packages
       -b, --backup    Move files that would be overwritten to ./backup
       -q, --quiet     Suppress wget/curl output
       -d, --download-only
                       Do not extract downloaded source
       -x, --extract   Unpack downloaded source (default)
       -u, --allow-unauthenticated
                       Do no attempt to verify source package signature
       --build         Build package with dpkg-buildpackage after download
       --path DIR      Check these directories in addition to the apt archive;
                       if DIR='' then clear current list (may be used multiple
                       times)
       --insecure      Do not check SSL certificates when downloading
       --no-cache      Disable server-side HTTP cache
       --no-conf       Don't read devscripts config files;
                       must be the first option given
       -h, --help      This message
       -V, --version   Version information

    Default settings modified by devscripts configuration files:
      (none)
    liw@exolobe1$ echo $?
    0
    liw@exolobe1$
--- /etc/devscripts.conf ---

--- ~/.devscripts ---
DEBSIGN_KEYID=5E8511F9
DSCVERIFY_KEYRINGS=/home/liw/.gnupg/pubring.gpg