Add a META.yml to the distribution. Your buildtool should be able to autogenerate it.
List all used modules in META.yml requires
Add a META.json to the distribution. Your buildtool should be able to autogenerate it.
Define the license if you are using in Build.PL. If you are using MakeMaker (Makefile.PL) you should upgrade to ExtUtils::MakeMaker version 6.31.
Split the distribution, or fix the version numbers to make them consistent (use the highest version number to avoid version downgrade).
This is not a critical issue. Currently mainly informative for the CPANTS authors. It might be removed later.