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

[Daniel Kahn Gillmor]

Package: devscripts
Version: 2.15.10
Severity: normal

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
Downloading http://bugs.debian.org/574672 ... bts: failed to download bugreport.cgi?bug=574672;msg=5;mbox=yes, skipping
bts: failed to download bugreport.cgi?bug=574672;mbox=yes;msg=12, skipping
(cached new version) 2/116
 [...]

every bug that it tries to download sees the same kind of error.

looking at http://bugs.debian.org/678613, the first concrete message
is msg=5.  when i try to fetch it myself, i get a zero-length file:

0 dkg at alice:~$ wget -q -S -O- 'http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=4;mbox=yes;bug=678613' 
  HTTP/1.1 200 OK
  Date: Tue, 05 Jan 2016 17:53:05 GMT
  Server: Apache
  Content-disposition: attachment; filename="bug_678613_message_4.mbox"
  Strict-Transport-Security: max-age=15552000
  Last-Modified: Fri, 27 Jun 2014 19:51:09 GMT
  X-Clacks-Overhead: GNU Terry Pratchett
  Content-Length: 0
  Keep-Alive: timeout=5, max=100
  Connection: Keep-Alive
  Content-Type: message/rfc822
0 dkg at alice:~$ 

Both --cache-mode=mbox and --cache-mode=min work fine, afaict.

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?

     --dkg

-- Package-specific info:

--- /etc/devscripts.conf ---

--- ~/.devscripts ---
Not present

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'testing'), (200, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages devscripts depends on:
ii  dpkg-dev     1.18.4
ii  libc6        2.21-6
ii  perl         5.22.1-3
pn  python3:any  <none>

Versions of packages devscripts recommends:
ii  apt                         1.1.10
ii  at                          3.1.18-2
ii  curl                        7.46.0-1
ii  dctrl-tools                 2.24-1
ii  debian-keyring              2015.11.30
ii  dput-ng [dput]              1.10
ii  dupload                     2.7.0
pn  equivs                      <none>
ii  fakeroot                    1.20.2-1
ii  file                        1:5.25-2
ii  gnupg                       1.4.20-1
ii  gnupg2                      2.1.10-3
ii  libdistro-info-perl         0.14
ii  libencode-locale-perl       1.05-1
ii  libjson-perl                2.90-1
ii  liblwp-protocol-https-perl  6.06-2
pn  libsoap-lite-perl           <none>
ii  liburi-perl                 1.69-1
ii  libwww-perl                 6.15-1
ii  lintian                     2.5.39.1
ii  man-db                      2.7.5-1
ii  patch                       2.7.5-1
ii  patchutils                  0.3.4-1
ii  python3-debian              0.1.27
ii  python3-magic               1:5.25-2
ii  sensible-utils              0.0.9
ii  strace                      4.10-3
ii  unzip                       6.0-20
ii  wdiff                       1.2.2-1+b1
ii  wget                        1.17.1-1
ii  xz-utils                    5.1.1alpha+20120614-2.1

Versions of packages devscripts suggests:
ii  build-essential              11.7
pn  cvs-buildpackage             <none>
ii  debbindiff                   44
ii  devscripts-el                35.12
pn  gnuplot                      <none>
ii  gpgv                         1.4.20-1
ii  gpgv2                        2.1.10-3
pn  libauthen-sasl-perl          <none>
pn  libfile-desktopentry-perl    <none>
ii  libnet-smtp-ssl-perl         1.03-1
pn  libterm-size-perl            <none>
ii  libtimedate-perl             2.3000-2
pn  libyaml-syck-perl            <none>
ii  mailutils [mailx]            1:2.99.98-2+b1
ii  mozilla-devscripts           0.42
pn  mutt                         <none>
ii  openssh-client [ssh-client]  1:7.1p1-5
ii  s-nail [mailx]               14.8.5-4
ii  svn-buildpackage             0.8.5+nmu1
ii  w3m                          0.5.3-26

-- debconf-show failed