We're calling `yum makecache` in `check_custom_repos_are_valid()` to check whether a repository is accessible (no typo in the repoid, repo metadata available under the baseurl, etc.). We should separate this cache making to a separate function, similarly to cache cleaning for which we have `clean_yum_metadata()`.

Related code:

• https://github.com/oamg/convert2rhel/blob/v1.1/convert2rhel/checks.py#L345
• https://github.com/oamg/convert2rhel/blob/v1.1/convert2rhel/pkghandler.py#L1125

Acceptance criteria:

• Move yum make-cache call from the check_custom_repos_are_valid to a separate function, for example to the repo.py module (move there the clean_yum_metadata() from the pkghandler.py module as well)
• Call this new yum make-cache functions before system checks, but after the cache cleaning

Upon further analysis of this task, we've realized that the `yum makecache` command under the `check_custom_repos_are_valid()` function is actually correct. That's the intent of calling the command - to see if the repos passed through the --enablerepo convert2rhel option are accessible.

There's one related issue though - that we don't necessarily clean the cache of the repo passed through the --enablerepo convert2rhel option. Because by default the `yum clean` command cleans the cache just for enabled repos.

Consider this scenario:

• I'm and admin preparing a CentOS Linux 7 system for a conversion to RHEL 7
• I have prepared a mirror of a RHEL 7 repo on an FTP server available on an internal company network
• I create an /etc/yum.repos.d/rhel7-on-our-ftp.repo file where I define a rhel-7-server-rpms repoid pointing to the RHEL 7 repo on the on-premise FTP server
• I make the repo disabled by default (enabled=0)
• I check whether the repo definition is ok by running '# yum info kernel --setopt=reposdir=/home/admin/conversion/ --enablerepo=rhel-7-server-rpms' and it works ok. That command generates a yum cache for this repo.
• Couple of hours later I run convert2rhel, not knowing the FTP server is down
• convert2rhel executes 'yum clean metadata' but that cleans cache of the enabled repos on the system only and the rhel-7-server-rpms is not enabled
• convert2rhel runs the custom repo validity check in which it executes

  yum makecache -v --setopt={*}.skip_if_unavailable=False --disablerepo="{\*}" --enablerepo=rhel-7-server-rpms

  and it returns 0 because it uses the cache generated hours ago

The above scenario show where the clean_yum_metadata() function is deficient - it does not clean cache of all the repos the convert2rhel works with.

Acceptance criteria:

• Clean yum cache (just metadata is sufficient) of all repos defined on the system, i.e. not only the enabled ones but also the disabled ones
  • This will make sure that convert2rhel works with fresh metadata even in the scenario depicted above