scp-dbus-service.py crashed with ImportError in __main__: No module named asyncconn

Can you run

sudo apt-get install --reinstall system-config-printer-common system-config-printer-gnome

Am 29.02.2012 16:42, schrieb Till Kamppeter:
> Can you run
>
> sudo apt-get install --reinstall system-config-printer-common system-
> config-printer-gnome

Just did.
I haven't seen this error in a while, so it may be fixed already.

So I am closing this. Re-open if the problem occurs again.

Reopening since I can trigger this error reasonably reliably on 12.04.

add-printer(21143) SelectMakeModel::getBestDriversFailed: Failed to get best drivers QDBusError("org.freedesktop.DBus.Error.Spawn.ChildExited", "Process /usr/bin/scp-dbus-service exited with status 1") QDBusMessage(type=MethodCall, service="org.fedoraproject.Config.Printing", path="/org/fedoraproject/Config/Printing", interface="org.fedoraproject.Config.Printing", member="GetBestDrivers", signature="", contents=("MFG:HP;MDL:Officejet Pro 8500 A909g;CMD:MLC,PCL,PML,DW-PCL,DESKJET,DYN;1284.4DL:4d,4e,1;CLS:PRINTER;DES:CB023A;SN:MY93O210V8;S:038080ec840010210068eb800008fb8000044c8003245cd001446cd000a41c8005a;Z:0102,0500000900000901a5e1019641022c41026161,0600,07000000000000000000000000,0b0000000000000000989b98ba0000987098a30000987098a4000098af98c5,0c0,10000000000000000000000000000000000000,12000,150;", "HP Officejet Pro 8500 A909g", "socket://192.168.111.99:9100") )

/usr/share/system-config-printer/asyncconn.py system-config-printer-gnome

This file needs to be moved to -common since it's used from there.

Sigh. But it used gtk, so it needs to refactoring. asyncipp.py, asyncpk1.py, and authconn.py need moving too.

Kubuntu's new print-manager uses scp-dbus-service, so getting this fixed in Quantal is rather important.

Till, can you have a look at this bug and fix from what Scott's told? Thanks :)

asyncconn.py, asyncipp.py, asyncpk1.py, and authconn.py provide a mechanism for authentication against CUPS. The modules provide especially non-blocking authentication dialogs and auto-select between authentication via IPP and PolicyKit. All the four files depend onm GTK, but only asyncipp.py and authconn.py actually produce GUI elements (not taking into account GUIs of test programs which are started by executing the module as a program itself, like via "python <module>.py"). asyncpk1.py only uses "gtk.gdk.threads_enter ()"/"gtk.gdk.threads_leave ()" pairs, and in asyncconn.py GTK is imported without need.

It will probably need major changes to separate out the GUI elements and make these four modules GUI-toolkit-independent.

It seems if one could somehow make system-config-printer only need asynchronous authentication via PolicyKit, for example by blocking out features which would use IPP or synchronous authentication (running s-c-p as root, administration of remote CUPS servers, ...) one could perhaps work around the GTK GUI elements. Then one would need to put the "import gtk" calls into "try:"/"except:" constructs.

Tim, Jiri, what do you think, is there an easy way to make scp-dbus-service.py and other authentication-needing parts of system-config-printer work in a GTK-free environment like Kubuntu?

I have checked further and found out that scp-dbus-service.py only uses authentication via asyncconn.py, never via asyncipp.py, asyncpk1.py, or authconn.py directly. So for all authentication access an auto-selection of IPP authentication (done by asyncipp.py and authconn.py) or PolicyKit authentication is done:

use_pk = ((host.startswith ('/') or host == 'localhost') and
                  os.getuid () != 0)

PoliciKit is chosen if the program is started by a non-root user and the CUPS host is local (either "localhost" or a socket). The PolicyKit authentication does not open any GTK windows.

Also note that the "import authconn" in asyncconn.py is bogus, there asyncconn.py does not use authconn.py directly.

The only use of the GTK module in asyncpk1.py are "gtk.gdk.threads_enter ()"/"gtk.gdk.threads_leave ()" pairs which should be made optional (only if gtk is present), removed, or replaced by something more general.

So one could do the following:

1. Make the KDE printer setup tool PolicyKit-only. For this let it error out (with an error dialog) when the user tries to start it as root and also ignore any remote CUPS servers set as default via client.conf and do not offer functionality to switch the CUPS server (If the default CUPS server is remote, try to access "localhost" or the local daemon via socket and if this does not work, error out with an error dialog). With all this, asyncconn will always select PolicyKit authentication.

2. Remove "import gtk" and "import authconn" in asyncconn.py

3. In ayncconn.py import only the one to be actually used of asyncipp and asyncpk1. If the import fails, let the creation of the Connection instance fail.

4. In asyncpk1.py bracket the "import gtk", "gtk.gdk.threads_enter ()", and "gtk.gdk.threads_leave ()" calls in "try: ... except: ...". In the "except:" blocks either do nothing or put any substitution for the "gtk.gdk.threads_enter ()"/"gtk.gdk.threads_leave ()" mechanism.

5. For the Ubuntu packaging move asyncconn.py and asyncpk1.py from the system-config-printer-gnome binary package into system-config-printer-common.

Scott, Tim, Jiri, WDYT about this solution?

Note that in the Ubuntu package the PolicyKit support is generally blocked out by a patch, due to bug 807261. I have done a quick check and the bug seems to be fixed. So the patch can be removed.

This bug was fixed in the package system-config-printer - 1.3.11+20120807-0ubuntu7

---------------
system-config-printer (1.3.11+20120807-0ubuntu7) quantal; urgency=low

  * debian/patches/33_scp-dbus-service-policy-kit-only-auth-on-non-gtk-systems.patch:
    Made asyncconn.py and asyncpk1.py working also without GTK, so that
    scp-dbus-service can be used on GTK-less systems like Kubuntu. Note that
    this requires authentication via PolicyKit and so scp-dbus-service can
    only run under conditions where PolicyKit is supported, which means that
    it must run as a non-root user and accessing a local CUPS daemon, via
    "localhost" or socket (LP: #902762).
  * debian/system-config-printer-common.install,
    debian/system-config-printer-gnome.install,
    debian/control: Moved asyncconn.py and asyncpk1.py from
    system-config-printer-gnome to system-config-printer-common
    (LP: #902762).
  * debian/patches/27_disable-policy-kit-support.patch: Removed, as
    cups-pk-helper is fixed now (See LP: #807261).
  * debian/patches/07_allow-also-nonfree-ppds-for-single-ppd-download.patch:
    Removed, as it is not needed any more. The patch
    30_driver-autodownload.patch overrides the onlyfree setting in
    the cupshelpers::openprinting module.
 -- Till Kamppeter <email address hidden> Wed, 12 Sep 2012 15:57:00 +0200

Scott, can you test the new system-config-printer package? Does it work this way as longs as you stay under supported conditions (printer setup tool started as non-root user and working on a local CUPS server)?

Tim, Jiri, this is the patch which I have applied to the current Ubuntu package. It is the simplest solution, one could do a better error handling if one of the two authentication methods fails, like gracefully erroring out or a failover to the other method.