Currently, it is not possible to use solr on platform.sh.

Basically, we set shards settings, where the hostname doesn't resolve inside the solr container at platform.sh.

Solution is either

1. Platform.sh may fix this by ensuring hostname provided by $PLATFORM_RELATIONSHIPS resolves in the solr container too, not only in the app container
2. Change ezplatform to not set these shard settings on a single-solr setup