Q:

Solr 6.1 warning: Couldn't add files to classpath

I freshly configured a Solr 6.1 server (actually a migration from version 4) and get a lot of warnings like:
WARN  (coreLoadExecutor-6-thread-2) [   ] o.a.s.c.SolrConfig Couldn't add files from C:\dev\solr-6.1.0\server\solr\configsets\foobar\..\..\..\dist filtered by solr-cell-\d.*\.jar to classpath: C:\dev\solr-6.1.0\server\solr\configsets\foobar\..\..\..\dist

or 
WARN  (coreLoadExecutor-6-thread-2) [   ] o.a.s.c.SolrConfig Couldn't add files from C:\dev\solr-6.1.0\server\solr\configsets\foobar\..\..\..\contrib\extraction\lib filtered by .*\.jar to classpath: C:\dev\solr-6.1.0\server\solr\configsets\foobar\..\..\..\contrib\extraction\lib

But: There are no *.jar files anywhere below C:\dev\solr-6.1.0\server\solr\configsets\foobar (in fact there is only a subdirectory conf with some .xml files) and the server is running fine so far, so I'm wondering what this warning is going to tell me. Can I just ignore it? Am I missing anything important?

A:

Thanks to Oyeme's comment I discovered that I included some example stuff in the solrconfig.xmls:
<lib dir="../../../contrib/extraction/lib" regex=".*\.jar"/>
<lib dir="../../../dist/" regex="solr-cell-\d.*\.jar"/>

<lib dir="../../../contrib/clustering/lib/" regex=".*\.jar"/>
<lib dir="../../../dist/" regex="solr-clustering-\d.*\.jar"/>

<lib dir="../../../contrib/langid/lib/" regex=".*\.jar"/>
<lib dir="../../../dist/" regex="solr-langid-\d.*\.jar"/>

<lib dir="../../../contrib/velocity/lib" regex=".*\.jar"/>
<lib dir="../../../dist/" regex="solr-velocity-\d.*\.jar"/>

Deleting these lines was the solution.

