There is no call to yum_base using 'cachedir' argument, so
while it work fine from a cursory look, that's useless code,
and so should be removed to clarify the code.
Using the rpm module prevent a uneeded fork, and permit
to skip the signature checking which slow down a bit the
operation, and which would be done by yum on installation
anyway.
Yum does not always update to latest package version unless metadata cache has expired. By runing yum makecache, we ensure the metadata cache has been updated.
Signed-off-by: René Moser <mail@renemoser.net>