I want warnings to be enabled on Travis but I don't to impose -Werror upon all my users – only Travis. How should I modify the generated travis.yml? I tried modifying the last invocation of cabal new-build, but it enabled warnings for all dependencies too, not just for my library (build log):

  # build & run tests, build benchmarks
- - cabal new-build -w ${HC} ${TEST} ${BENCH} all
+ - cabal new-build --ghc-options=-Werror -w ${HC} ${TEST} ${BENCH} all