[Yum-devel] [PATCH] Checks if we have read and write access in the current directory. If not, chdir to /. BZ 698795

[Nick Jacek]

As reported on Bugzilla, yum will fail silently if it is run from a
rootsquashed nfs mount, since rpm will not have any read or write
access.  Due to a previous patch, yum will already correctly report
that the operations fail, but it will not give any explanation as to
why.  With this patch, most operations should simply complete
successfully, but note that changing the working directory will break
things such as specifying rpms to install via relative paths.

Arguably, it might be better to instead just report to the user that
rpm has run into errors since it doesn't have the necessary
permissions, but ifaict there's not really any way to do that.  When
ts.run() is called both in testing the transaction and actually
running the transaction it returns an empty list, which is supposed
to indicate that it has experienced non-fatal errors. Since ifaict
there's no way to tell what the errors are, in this case we can't
report them to the user.  Furthermore, the output of rpm is sent to a
temporary file to be logged. It seems that the output can be
displayed to the user via certain callbacks, but in this case rpm
doesn't call any callbacks at all.  So it seems that the temporary
file is just deleted.