diff-lcs has changed its format in 1.4

See: rspec/rspec-support#421

Author: benoittgt

travis/.travis.yml

@@ -36,6 +36,8 @@ matrix:
   include:
     - rvm: jruby-1.7
       env: JRUBY_OPTS='--dev --1.8'
+    - rvm: 2.7.1
+      env: DIFF_LCS_VERSION="~> 1.3.0"
   allow_failures:
     - rvm: jruby-head
     - rvm: ruby-head