Add a bunch of guards around function calls like open() and stat() to ensure
we are not going to get ourselves a python error. This made implementing and
testing the new upgrade045 pactest much easier, as its whole purpose was to
create a dead symlink and debug a segfault of pacman (which caused no DB
entries to be written) to support the previously checked in fix for FS#9235
(commit 0c2206f542). Both of these cases are
now non-fatal in pactest.
Signed-off-by: Dan McGee <dan@archlinux.org>
