minor #1833 work around autoloading issues with Composer 1.6.1 (xabbuh)

This PR was merged into the 2.3-dev branch.

Discussion
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work around autoloading issues with Composer 1.6.1

Commits
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52ba336 work around autoloading issues with Composer 1.6.1

Author: xabbuh

.travis.yml

@@ -30,6 +30,10 @@ matrix:
 
 before_install:
   - if [ "$TRAVIS_PHP_VERSION" != "hhvm" ]; then phpenv config-rm xdebug.ini; fi
+
+  # temporary workaround until https://github.com/composer/composer/issues/6977 is resolved
+  - composer self-update 1.5.6
+
   - if [ "$DEPENDENCIES" != "" ]; then composer config minimum-stability $DEPENDENCIES; fi
   - if [ "$SYMFONY_LTS" != "" ]; then composer require --dev --no-update symfony/lts=$SYMFONY_LTS; fi