Comment 8 for bug 320273

Same error here!
It fails on some packages, like wine on my case:

apt-build install wine1.2
wine1.2 will not be built because it doesn't have a source package.
Missing source package name for source_by_source().

*however apt-get source gets the package happily

------------------------------------------------------------------------------
apt-get source wine
Leyendo lista de paquetes... Hecho
Creando árbol de dependencias
Leyendo la información de estado... Hecho
Tome «wine1.2» como paquete fuente en vez de «wine»
Necesito descargar 22,7MB de archivos fuente.
Des:1 http://archive.ubuntu.com/ubuntu/ maverick-updates/universe wine1.2 1.2.1-0ubuntu1 (dsc) [2379B]
Des:2 http://archive.ubuntu.com/ubuntu/ maverick-updates/universe wine1.2 1.2.1-0ubuntu1 (tar) [22,5MB]
7% [2 wine1.2 1658kB/22,5MB 7%]^C

---------------------------------------------------------------------------------------------------------------------------
apt-cache policy wine1.2
wine1.2:
  Instalados: 1.2.1-1ubuntu1
  Candidato: 1.2.1-1ubuntu1
  Tabla de versión:
 *** 1.2.1-1ubuntu1 0
        100 /var/lib/dpkg/status
     1.2.1-0ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ maverick-updates/universe amd64 Packages
     1.2-0ubuntu9 0
        500 http://archive.ubuntu.com/ubuntu/ maverick/universe amd64 Packages
N: Ignoring file 'apt-build' in directory '/etc/apt/sources.list.d/' as it has no filename extension

----------------------------------------------------------------------------------------------------------------------------------------
# apt-cache show wine1.2
Package: wine1.2
Priority: optional
Section: universe/otherosfs
Installed-Size: 84820
Maintainer: Ubuntu MOTU Developers <email address hidden>
Original-Maintainer: Scott Ritchie <email address hidden>
Architecture: amd64
Version: 1.2-0ubuntu9
Replaces: libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Provides: wine
Depends: procps, binfmt-support (>= 1.1.2), ia32-libs (>= 1.6), lib32asound2 (>> 1.0.14), libc6-i386 (>= 2.6-1), lib32nss-mdns (>= 0.10-3), debconf (>= 0.5) | debconf-2.0
Pre-Depends: dpkg (>= 1.14.12ubuntu3)
Recommends: ttf-symbol-replacement, ttf-liberation, winbind, wine1.2-gecko, ttf-mscorefonts-installer, gnome-exe-thumbnailer | kdebase-runtime, cups-bsd, winetricks, wisotool
Suggests: xdg-utils
Conflicts: binfmt-support (<< 1.1.2), libwine, libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Filename: pool/universe/w/wine1.2/wine1.2_1.2-0ubuntu9_amd64.deb
Size: 10956368
MD5sum: 01cc9314a22554f85fbcd65c3ce39b5d
SHA1: cac1fea2ba44819bdef8db98e5f15066380c3dc4
SHA256: fea7c197faf8cf5452fd51a7c63d56e1ad1e16910d298956f1e822ecc016ccb9
Description-es: Capa de compatibilidad con Microsoft Windows (emulador binario y biblioteca)
 Wine es una capa de compatibilidad para ejecutar aplicaciones de Windows
 en Linux. Las aplicaciones se ejecutan a la máxima velocidad sin necesidad
 de emulación de la CPU. No hace falta tener Microsoft Windows para poder
 usar Wine, pero puede usar los archivos DLL nativos en lugar de los suyos
 si están disponibles.
 .
 Este paquete incluye un cargador de programas para ejecutar programas
 Windows sin necesidad de modificarlos, así como la versión libre del API
 de Windows del proyecto Wine para ejecutar programas portados desde
 Windows.
 .
 This package is based on a recent Wine beta. While many more applications
 will work, there may be some loss of functionality compared with the
 stable release provided by the regular wine package.
Homepage: http://www.winehq.org/
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu

Package: wine1.2
Priority: optional
Section: universe/otherosfs
Installed-Size: 85328
Maintainer: Ubuntu MOTU Developers <email address hidden>
Original-Maintainer: Scott Ritchie <email address hidden>
Architecture: amd64
Version: 1.2.1-0ubuntu1
Replaces: libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Provides: wine
Depends: procps, binfmt-support (>= 1.1.2), ia32-libs (>= 1.6), lib32asound2 (>> 1.0.14), libc6-i386 (>= 2.6-1), lib32nss-mdns (>= 0.10-3), debconf (>= 0.5) | debconf-2.0
Pre-Depends: dpkg (>= 1.14.12ubuntu3)
Recommends: ttf-symbol-replacement, ttf-liberation, winbind, wine1.2-gecko, ttf-mscorefonts-installer, gnome-exe-thumbnailer | kdebase-runtime, cups-bsd, winetricks, wisotool
Suggests: xdg-utils
Conflicts: binfmt-support (<< 1.1.2), libwine, libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Filename: pool/universe/w/wine1.2/wine1.2_1.2.1-0ubuntu1_amd64.deb
Size: 11045552
MD5sum: 7091f4b7e3b8245f5c0b47c2169085ca
SHA1: e5952e246c4062813110324bec82a863fe43cc58
SHA256: 9c7106336ca1301f6be27f6345412bb204430c3c0aed0126a734aa17830f4a7c
Description: Microsoft Windows Compatibility Layer (Binary Emulator and Library)
 Wine is a compatibility layer for running Windows applications on Linux.
 Applications are run at full speed without the need of cpu emulation. Wine
 does not require Microsoft Windows, however it can use native system dll
 files in place of its own if they are available.
 .
 This package includes a program loader for running unmodified Windows executables
 as well as the Wine project's free version of the Windows API for running programs
 ported from Windows.
 .
 This package is based on a recent Wine beta. While many more applications will
 work, there may be some loss of functionality compared with the stable release
 provided by the regular wine package.
Homepage: http://www.winehq.org/
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Origin: Ubuntu

Package: wine1.2
Status: install ok installed
Priority: optional
Section: otherosfs
Installed-Size: 85348
Maintainer: Ubuntu MOTU Developers <email address hidden>
Architecture: amd64
Version: 1.2.1-1ubuntu1
Replaces: libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Provides: wine
Depends: procps, binfmt-support (>= 1.1.2), ia32-libs (>= 1.6), lib32asound2 (>> 1.0.14), libc6-i386 (>= 2.6-1), lib32nss-mdns (>= 0.10-3), debconf (>= 0.5) | debconf-2.0
Pre-Depends: dpkg (>= 1.14.12ubuntu3)
Recommends: ttf-symbol-replacement, ttf-liberation, winbind, wine1.2-gecko, ttf-mscorefonts-installer, gnome-exe-thumbnailer | kdebase-runtime, cups-bsd, winetricks, wisotool
Suggests: xdg-utils
Conflicts: binfmt-support (<< 1.1.2), libwine, libwine-alsa, libwine-arts, libwine-capi, libwine-cms, libwine-esd, libwine-gl, libwine-gphoto2, libwine-jack, libwine-ldap, libwine-nas, libwine-print, libwine-sane, libwine-twain, ttf-tahoma-replacement, wine (<< 1.1.36-0ubuntu2), wine-doc, wine-utils, wine1.0, winesetuptk, xwine
Conffiles:
 /etc/xdg/menus/applications-merged/wine.menu d15dadc3527b2c6dca96023a5351aedc
Description: Microsoft Windows Compatibility Layer (Binary Emulator and Library)
 Wine is a compatibility layer for running Windows applications on Linux.
 Applications are run at full speed without the need of cpu emulation. Wine
 does not require Microsoft Windows, however it can use native system dll
 files in place of its own if they are available.
 .
 This package includes a program loader for running unmodified Windows executables
 as well as the Wine project's free version of the Windows API for running programs
 ported from Windows.
 .
 This package is based on a recent Wine beta. While many more applications will
 work, there may be some loss of functionality compared with the stable release
 provided by the regular wine package.
Homepage: http://www.winehq.org/
Original-Maintainer: Scott Ritchie <email address hidden>