travis: use community supported language

Switch to the "community supported" Nix version of Travis.

.travis.yml

@@ -1,22 +1,18 @@
+language: nix
 matrix:
     include:
         - os: linux
-          language: generic
+          sudo: false
-          sudo: required
-          dist: trusty
           script:
               - ./maintainers/scripts/travis-nox-review-pr.sh verify
               - ./maintainers/scripts/travis-nox-review-pr.sh check
               - ./maintainers/scripts/travis-nox-review-pr.sh tarball
         - os: linux
-          language: generic
           sudo: required
           dist: trusty
           script: ./maintainers/scripts/travis-nox-review-pr.sh pr
         - os: osx
-          language: generic
           osx_image: xcode7.3
           script: ./maintainers/scripts/travis-nox-review-pr.sh pr
-install: ./maintainers/scripts/travis-nox-review-pr.sh install
 git:
     depth: 1

maintainers/scripts/travis-nox-review-pr.sh

@@ -1,14 +1,6 @@
 #! /usr/bin/env bash
 set -e
 
-# This should make Curl silent
-# but download-from-binary-cache doesn't respect
-export NIX_CURL_FLAGS=-sS
-
-if [ -d $HOME/.nix-profile ]; then
-    source $HOME/.nix-profile/etc/profile.d/nix.sh
-fi
-
 while test -n "$1"; do
 
     # tell Travis to use folding
@@ -16,23 +8,6 @@ while test -n "$1"; do
 
     case $1 in
 
-        install)
-            echo "=== Installing Nix..."
-
-            curl -sS https://nixos.org/nix/install | sh
-
-            # Make sure we can use hydra's binary cache
-            sudo mkdir /etc/nix
-            echo "build-max-jobs = 4" | sudo tee /etc/nix/nix.conf > /dev/null
-
-            # Make sure we can execute within /tmp in Linux
-            if [ "$TRAVIS_OS_NAME" == "linux" ]; then
-                sudo mount -o remount,exec /run
-                sudo mount -o remount,exec /run/user
-                sudo mount > /dev/null
-            fi
-            ;;
-
         verify)
             echo "=== Verifying that nixpkgs evaluates..."