  [javadoc] Generating Javadoc
  [javadoc] Debian build on Java 9+ detected: Adding the --ignore-source-errors option
  [javadoc] Javadoc execution
  [javadoc] Loading source files for package org.apache.lucene.search.grouping...
  [javadoc] Constructing Javadoc information...
  [javadoc] Standard Doclet version 10.0.1
  [javadoc] Building tree for all the packages and classes...
  [javadoc] javadoc: warning - You have not specified the version of HTML to use.
  [javadoc] The default is currently HTML 4.01, but this will change to HTML5
  [javadoc] in a future release. To suppress this warning, please specify the
  [javadoc] version of HTML used in your documentation comments and to be
  [javadoc] generated by this doclet, using the -html4 or -html5 options.
  [javadoc] /build/lucene-solr-PsnBQG/lucene-solr-3.6.2+dfsg/lucene/contrib/grouping/src/java/org/apache/lucene/search/grouping/AbstractFirstPassGroupingCollector.java:92: warning - invalid usage of tag <
  [javadoc] /build/lucene-solr-PsnBQG/lucene-solr-3.6.2+dfsg/lucene/contrib/grouping/src/java/org/apache/lucene/search/grouping/BlockGroupingCollector.java:287: warning - invalid usage of tag <
  [javadoc] /build/lucene-solr-PsnBQG/lucene-solr-3.6.2+dfsg/lucene/contrib/grouping/src/java/org/apache/lucene/search/grouping/package.html:163: warning - invalid usage of tag &
  [javadoc] Building index for all the packages and classes...
  [javadoc] Building index for all classes...
  [javadoc] Generating /build/lucene-solr-PsnBQG/lucene-solr-3.6.2+dfsg/lucene/build/docs/api/contrib-grouping/help-doc.html...
  [javadoc] 4 warnings
