travis-ci: pin rubygems version to 2.7.8 Signed-off-by: Masahiro Nakagawa <repeatedly@gmail.com>
travis-ci: pin rubygems version to 2.7.8
Signed-off-by: Masahiro Nakagawa <0f51a8c574c157b13d3ee3d2579e24fcb2f5df0d@gmail.com>

htgc/fluent-plugin-kafka