bzr should use apport to actually file bugs

[Martin Pool]

As of bzr 2.1 (post bug 389328) Bazaar uses the apport library to make a crash file in ~/.cache/crash. However, it would probably be better if we let apport do the whole job of actually filing the bug into Launchpad.

Problems at the moment:
* the user has to manually get the file and attach it to a bug report
* the file is not unpacked on Launchpad, so developers have to manually dig through the crash file to see the traceback
* we don't suggest a good summary line so many of them are contentfree like 'bzr crashes' <https://bugs.edge.launchpad.net/bzr/+bug/380973>

This bug is similar to <https://bugs.edge.launchpad.net/ubuntu/+source/bzr/+bug/391015> and they could be fixed together, but it's perhaps larger in scope.

There are a few different cases we have to think about:

0- people on Ubuntu from an official distro version of bzr
1- people on Ubuntu with a ppa version of bzr
2- people running from source on any platform
3- people on another unix-like platform running from the installer package
4- people Windows running from the installer

The work that seems to need to be done, some discussed in bug 391015, includes:

* Ubuntu wants to disable bug filing once the distrorelease is frozen; we're still interested in bug reports though
* we should probably default to filing them against bzr upstream not the bzr distro package

For people running from source it may be reasonable to assume they're developers or at least nerdy and just want to see the traceback.

[Martin Pool (mbp)]

On platforms where we can count on system apport support (so at least Ubuntu and maybe more) the intended behaviour is:

When an error is caught at the top level in bzr, write all the interesting information (including a list of plugins etc) into the systemwide apport crash directory (/var/crash), tell the user briefly what happened and that apport can be used to report a bug, and then exit cleanly.

When the error is not caught (eg a segfault) apport should catch this in the usual way and write a crash file.

After the crash file is written out, apport should notice it and ask the user if they want to report a bug either through a gui or apport-cli. This should happen even if it's in an Ubuntu release where automatic bug reporting is generally turned off, and the bug should be filed against upstream bzr. (Which is partly handled by the yet-unapplied patch in bug 391015.)

[Martin Pool (mbp)]

https://code.edge.launchpad.net/~mbp/bzr/apport/+merge/18341

[Martin Pool (mbp)]

After we land this we can use the apport-based de-duper described in http://people.canonical.com/~pitti/bugpatterns/README