[ticket/11060] Make sure pyrus can install everything on travis

This is needed so it can install symfony/yaml from a new channel.

PHPBB3-11060

.travis.yml

@@ -12,6 +12,7 @@ before_script:
   - sh -c "if [ '$DB' = 'postgres' ]; then psql -c 'DROP DATABASE IF EXISTS phpbb_tests;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'postgres' ]; then psql -c 'create database phpbb_tests;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'mysql' ]; then mysql -e 'create database IF NOT EXISTS phpbb_tests;'; fi"
+  - pyrus set auto_discover 1
   - pyrus install --force phpunit/DbUnit
   - phpenv rehash
   - cd phpBB