Solr is distributed with a solrconfig.xml which includes several examples of additional libraries. These libraries are not included with DSpace, and the <lib ... /> directives pointing to them thus cause error messages at core startup if they are not commented out or removed. Most of the cores configured with DSpace have been cleaned up, but the authority core has not. The resulting messages seem harmless but are confusing.
This was most recently reported today by Dr Ir Francis Brouns in dspace-tech.