Travis builds fail because of a segmentation fault

[MutazAshhab]

In previous pull requests (now closed and un-merged) Travis, the CI tool, failed to complete the build as it ran into a segmentation fault while installing the sassc gem.

Build #2304 https://app.travis-ci.com/github/openaustralia/publicwhip/builds/246832799#L821.

[MutazAshhab]

A solution that was discussed and worked for other developers is adding this snippet to config/initializers/assets.rb

Rails.application.config.assets.configure do |env|
  env.export_concurrent = false
end

mentioned here sass/sassc-ruby#197 (comment)

[MutazAshhab]

In a previous PR (#1350) builds without this change would fail build 2304.1, after the change was pushed to that PR the build succeeded build 2311