Subject: | Should not specify PREREQ_FATAL |
https://metacpan.org/source/TVIGNAUD/Gtk3-Notify-0.01/Makefile.PL#L23 specifies PREREQ_FATAL=>1.
This should not be done, as this prevents automatic installers like CPAN.pm from automatically installing all specified dependencies. Note also that the ExtUtils::MakeMaker "strongly discourage" the use of this parameter.