Required environment variables:
ET_DB_USER=<string>
ET_DB_PASS=<string>
ET_READ_DB=<string>
ET_EVENT_DB=<string>
ET_TEST_READ_DB=<string>
ET_TEST_EVENT_DB=<string>
ET_DB_HOST=<string>
ET_DNS_ADDR=<string>
ET_DB_POOL_SIZE=<integer>
ET_HTTP_PORT=<integer>
ET_SECRET_KEY_BASE=<string>