problems resolving prerequisites on 5.6

[karenetheridge]

In this build -- https://travis-ci.org/libwww-perl/LWP-MediaTypes/jobs/516030879

In the cpan-install --deps section, necessary prerequisites are not found and installed. There seems to be an issue with bootstrapping CPAN.pm. (cpanm is not being used here? I think it does have some 5.6 support.)

Additionally, this warning occurs:

Can't use string ("0") as a HASH ref while "strict refs" in use at /home/travis/travis-perl-helpers/bin/cpan-prereqs line 60.

Is there a different .travis.yml configuration that can be used to make prerequisite installs work better on 5.6?