make smart show non-cryptic error message on path noth available

[Rehan Khan]

Imported: http://tracker.labix.org/issue366

Reason: Issue Review. Bug. Better file/error handling required?

further details: https://blueprints.launchpad.net/smart/+spec/bug-reporting-migration

msg1318 (view) Author: casualprogrammer Date: 2008-02-16.19:38:47

For space reasons I replaced the directory /var/lib/smart/packages/ with a
symbolic link to an external (firewire) drive with ample space.

While running smart update with the drive not present, smart issues the
following message:

Traceback (most recent call last):

  File "/usr/lib/python2.5/site-packages/smart/interfaces/gtk/interactive.py",
line 180, in callback
    exec code in globals

  File "<callback>", line 1, in <module>

  File "/usr/lib/python2.5/site-packages/smart/interfaces/gtk/interactive.py",
line 424, in applyChanges
    if self._ctrl.commitTransaction(transaction, confirm=confirm):

  File "/usr/lib/python2.5/site-packages/smart/control.py", line 500, in
commitTransaction
    return self.commitChangeSet(trans.getChangeSet(), caching, confirm)

  File "/usr/lib/python2.5/site-packages/smart/control.py", line 545, in
commitChangeSet
    caching)

  File "/usr/lib/python2.5/site-packages/smart/control.py", line 632, in
fetchPackages
    os.makedirs(localdir)

  File "/usr/lib/python2.5/os.py", line 172, in makedirs
    mkdir(name, mode)

OSError: [Errno 17] File exists: '/var/lib/smart/packages/'

While the last line is probably the result of smart not being able to create the
packages directory because of the existing link, it could state that a link
exists whose target is missing, instead of this correct but rather cryptic message.