.travis.yml: add "sudo: required" to opt out of containers

Changed files
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.travis.yml
··· 1 1 language: python 2 2 python: "3.4" 3 + sudo: required 3 4 before_install: ./maintainers/scripts/travis-nox-review-pr.sh nix 4 5 install: ./maintainers/scripts/travis-nox-review-pr.sh nox 5 6 script: ./maintainers/scripts/travis-nox-review-pr.sh build