Handle the situation where there are broken dependencies on the client

[Andreas Hasenack]

We need to somehow handle the situation where there are broken dependencies on the client.

For example, I broke landscape-common by removing python-smartpm with --force-depends. I then added USE_APT_FACADE=1 to the landscape-client initscript and restarted it, so it would use apt.

apt is currently complaining that there are problems:

root@ls1-lucid:~# apt-get install libxml2
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run `apt-get -f install' to correct these:
The following packages have unmet dependencies:
  landscape-common: Depends: python-smartpm (>= 1.2-4) but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

The -f option suggests the right thing which is to install python-smartpm:

root@ls1-lucid:~# apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  python-crypto clouddeck python-pyasn1 python-chameleon python-openid python-zope.component libarchive1 python-transaction python-encutils erlang-inets erlang-snmp
  rrdtool bind9utils python-twisted-runner erlang-mnesia librrd4 python-txstatsd python-zope.event python-txaws python-lxml erlang-os-mon postgresql-client-8.4
  apache2-mpm-prefork rabbitmq-server libcap2-bin python-z3c.pt procmail python-genshi python-zope.datetime python-z3c python-psutil python-tz python-convoy libhal1
  hal python-commandant python-psycopg2 libsmi2ldbl python-twisted-lore python-twisted-conch python-twisted-news libhal-storage1 python-twisted python-nevow
  squid-common python-dateutil python-txamqp python-cssutils python-zope3 python-epsilon python-ordereddict postgresql-client erlang-crypto python-egenix-mxdatetime
  postgresql-client-common reprepro libc-ares2 liblua5.1-0 python-egenix-mxtools libpq5 erlang-ssl hal-info erlang-runtime-tools postgresql-plpython-8.4
  ttf-ubuntu-font-family python-storm postgresql-common squid-langpack postgresql-8.4 erlang-base erlang-public-key
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
  python-smartpm
The following NEW packages will be installed:
  python-smartpm
0 upgraded, 1 newly installed, 0 to remove and 3 not upgraded.
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Landscape, however, when trying to upgrade libxml2, will actually remove landscape-common and landscape-client (see screenshot).

I'm not sure what the proper action should be here. Some thoughts, in no particular order:
a) Ignore the error, since it doesn't affect libxml2 and its dependencies. It's what smart does.
b) Detect the broken situation, run the equivalent of apt-get -f install and present that to the user, including the original request. So, this activity would become install libxml2 and python-smartpm (and whatever other dependencies arise from that)
c) Cumbersome, but have some sort of special package activity that would just run the equivalent of apt-get -f install in these situations, and perhaps an alert about it (computer foo has dependency problems).