Merge pull request #2326 from mikerite/fix_travis_macos

Fix Travis CI build

.travis.yml

@@ -14,6 +14,15 @@ env:
    - secure: dj8SwwuRGuzbo2wZq5z7qXIf7P3p7cbSGs1I3pvXQmB6a58gkLiRn/qBcIIegdt/nzXs+Z0Nug+DdesYVeUPxk1hIa/eeU8p6mpyTtZ+30H4QVgVzd0VCthB5F/NUiPVxTgpGpEgCM9/p72xMwTn7AAJfsGqk7AJ4FS5ZZKhqFI=
    - RUST_BACKTRACE=1
 
+before_install:
+ - |
+    # work-around for issue https://github.com/travis-ci/travis-ci/issues/6307
+    # might not be necessary in the future
+    if [ "$TRAVIS_OS_NAME" == "osx" ]; then
+     command curl -sSL https://rvm.io/mpapis.asc | gpg --import -
+     rvm get stable
+    fi
+
 install:
   - . $HOME/.nvm/nvm.sh
   - nvm install stable