Bug#810021: devscripts: [bts] bts --cache-mode=full cache fails when fetching empty msg parts?

[Adam D. Barratt]

On Tue, 2016-01-05 at 12:54 -0500, Daniel Kahn Gillmor wrote:
> 0 dkg at alice:~$ bts --cache --cache-mode=full cache src:gnupg2
> Downloading http://bugs.debian.org/src:gnupg2 ... (cached new version) 
> Downloading http://bugs.debian.org/678613 ... bts: failed to download bugreport.cgi?msg=4;mbox=yes;bug=678613, skipping
> bts: failed to download bugreport.cgi?mbox=yes;msg=9;bug=678613, skipping
> (cached new version) 1/116
[...]
> Sorry to not have more pointers about what's going wrong here.  Maybe
> something changed in some perl module about "success" or "failure"
> when the file fetched has 0 length?

As far as I can tell, nothing's changed in terms of the code - bts has
always regarded a 0-byte file as a failure. The oldest machine I have to
hand to check is wheezy, which has

	if ($response->is_success) {
            my $content_length = defined $response->content ?
                length($response->content) : 0;
            if ($content_length == 0) {
                warn "$progname: failed to download $ref, skipping\n";

Presumably only "cache-mode=full" causes the "useless messages" to be
downloaded. What I'm not sure about is whether the BTS has always
presented those files as 0-bytes and, if so, why it bothers linking to
the mbox to begin with; the "full text" (i.e. non-mbox) versions appear
to be populated as expected.

Regards,

Adam