Bug#726498: gnome-session-bin 3.8 breaks gdm 3.4

[chrysn]

Package: gnome-session-bin
Version: 3.8.4-2
Severity: serious

upgrading gnome-session-bin from 3.4.2.1-4 to 3.8.4-2 makes gdm3
3.4.1-9+b1 not work any more, without declaring a breaks relationship.

/var/log/gdm3/:0-greeter.log contains only this line:

** (gnome-session:5465): WARNING **: Unknown option --start

after downgrading gnome-session-bin to 3.4 again, things work again, and
the --start line doesn't occur any more. (instead, :0-greeter.log gets
filled with other stuff).

i think that g-s-b 3.8 should Breaks: gdm3 (<< 3.8), because (quoting
policy #7.3) "such a Breaks is induced in a version of an [...]
dependency which violates an assumption [...] in earlier versions of the
broken package [...]".

best regards
chrysn

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

Kernel: Linux 3.10-2-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages gnome-session-bin depends on:
ii  dbus-x11                                     1.6.16-1
ii  dconf-gsettings-backend [gsettings-backend]  0.16.1-1
ii  gsettings-desktop-schemas                    3.8.2-2
ii  libc6                                        2.17-93
ii  libcairo2                                    1.12.16-2
ii  libdbus-1-3                                  1.6.16-1
ii  libdbus-glib-1-2                             0.100.2-1
ii  libgdk-pixbuf2.0-0                           2.28.2-1
ii  libgl1-mesa-glx [libgl1]                     9.1.7-1
ii  libglib2.0-0                                 2.38.0-1
ii  libgnome-desktop-3-7                         3.8.4-2
ii  libgtk-3-0                                   3.8.5-1
ii  libice6                                      2:1.0.8-2
ii  libjson-glib-1.0-0                           0.16.2-1
ii  libsm6                                       2:1.2.1-2
ii  libupower-glib1                              0.9.22-1
ii  libx11-6                                     2:1.6.2-1
ii  libxau6                                      1:1.0.8-1
ii  libxcomposite1                               1:0.4.4-1
ii  libxrender1                                  1:0.9.8-1
ii  upower                                       0.9.22-1

gnome-session-bin recommends no packages.

gnome-session-bin suggests no packages.

-- no debconf information

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