Don't create a new Travis cache on every build.
Don't create a new Travis cache on every build.

These two files are changed on every build, even if nothing has changed.

The Travis docs seem to be a little out of date in this regard (see
https://github.com/travis-ci/docs-travis-ci-com/pull/611#issuecomment-321391538),
and this is the recommended fix.

charleskorn/batect,charleskorn/batect,charleskorn/batect,charleskorn/batect,charleskorn/batect