Permission denied SystemError when launching

[Michael Terry]

Binary package hint: ubuntuone-client

ubuntuone-control-panel-gtk crashes when launching with the following stacktrace:

Traceback (most recent call last):
  File "/usr/bin/ubuntuone-control-panel-gtk", line 65, in <module>
    switch_to=options.switch_to, alert=options.alert)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/gui.py", line 1578, in __init__
    self.control_panel = ControlPanel(main_window=self)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/gui.py", line 1527, in __init__
    self.management = ManagementPanel(main_window=main_window)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/gui.py", line 1464, in __init__
    self.services.load()
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/logger.py", line 76, in inner
    res = f(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/gui.py", line 1159, in load
    logger.info('load: has_desktopcouch? %r', self.has_desktopcouch)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/gui.py", line 1126, in has_desktopcouch
    return self.package_manager.is_installed(self.DESKTOPCOUCH_PKG)
  File "/usr/lib/pymodules/python2.7/ubuntuone-control-panel/ubuntuone/controlpanel/gtk/package_manager.py", line 48, in is_installed
    cache = apt.Cache()
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 88, in __init__
    self.open(progress)
  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 130, in open
    self._list.read_main_list()
SystemError: E:Opening /etc/apt/sources.list.d/private-ppa.launchpad.net_commercial-ppa-uploaders_volleybrawl_ubuntu.list - ifstream::ifstream (13: Permission denied)

[Michael Terry (mterry)]

(this was in a guest session)

[Natalia Bidart (nataliabidart)]

I'm assigning to the ubuntuone-control-panel project, since this trace is caused in that source code.

The Ubuntu One control panel uses apt.cache library to query for package availability, but that library is crashing if it can't read a sources file that has some custom/restricted permission set.

I think we should make the control panel robust in this situation so it doesn't break, but we also need that the underlying library handles this case properly.

[Natalia Bidart (nataliabidart)]

I filed bug #746625 for python-apt.

[Natalia Bidart (nataliabidart)]

So, python-apt closed the bug as Invalid. We may be more robust on the control panel side, but there isn't much else we can do.

[Michael Vogt (mvo)]

The reason some of the files are 640 is because they contain private ppas. What do you use python-apt for in this context? Maybe we can find a solution that works even with the permission problem.

[Natalia Bidart (nataliabidart)]

Hi Michael,

We use python-apt to access the Cache and check if desktopcouch-ubuntuone (and some other couchdb packages) are installed. We need to do so to enable some replication services, and those packages are not shipped in the CD anymore (so is very likely they are not present).

We could catch the exception, but if the underlying layer will fail without going over the sources that does have read perm, there isn't much we can do. The apt guys suggest that we shouldn't be setting 640 as file mode nor be adding passwords in the sources files (see bug #746625).