Try to expose Composer's autoloading.

tests/scripts/travis_setup.sh

@@ -35,6 +35,8 @@ phpenv rehash
 drush dl --yes drupal
 cd drupal-*
 drush si minimal --db-url=mysql://drupal:drupal@localhost/drupal --yes
+# Needs to make things from Composer be available (PHP CS, primarily)
+echo "include_once $HOME/.composer/vendor/autoload.php;" >> sites/default/settings.php
 drush runserver --php-cgi=$HOME/.phpenv/shims/php-cgi localhost:8081 &>/dev/null &
 ln -s $ISLANDORA_DIR sites/all/modules/islandora
 mv sites/all/modules/islandora/tests/travis.test_config.ini sites/all/modules/islandora/tests/test_config.ini