Provide a better failure message when the rat check fails

patch by Mick Semb Wever; reviewed by David Capwell, Ekaterina Dimitrova for CASSANDRA-16620

.build/build-rat.xml

@@ -67,7 +67,10 @@
                      <exclude NAME="**/LICENSE.md"/>
             </fileset>
         </rat:report>
-        <fail message="Some files have missing or incorrect license information. Check RAT report in ${build.dir}/rat.txt for more details!">
+        <exec executable="grep" outputproperty="rat.failed.files" failifexecutionfails="false">
+            <arg line="-A5 'Unapproved licenses' ${build.dir}/rat.txt"/>
+        </exec>
+        <fail message="Some files have missing or incorrect license information. Check RAT report in ${build.dir}/rat.txt for more details! \n ${rat.failed.files}">
             <condition>
                 <and>
                     <not>

.gitignore

@@ -8,6 +8,7 @@ logs/
 data/
 conf/hotspot_compiler
 doc/cql3/CQL.html
+pylib/src/
 
 # C* debs
 build-stamp
@@ -26,7 +27,7 @@ debian/files
 # IntelliJ
 .idea/
 *.eml
-*.iml
+**/*.iml
 *.ipr
 *.iws