Bug 30731: Unit tests

Bug 30731: Unit tests

Installer_pm.t can safely be discarded, having Installer_PerlModules.t.

Note: Without the second patch, the test about versions_info being silent
might fail. With the second patch, it should pass.
Note that since the order of requiring the cpan modules varies (without
the second patch), the results (potential warnings) vary too.

Test plan:
Run t/Installer_PerlModules.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>