Fix NoSuchMethodError on processing errors in pmd-compat6

(cherry picked from commit f73d75d5a3)

pmd-compat6/src/it/pmd-for-java/exception_ruleset.xml

@@ -0,0 +1,16 @@
+<ruleset xmlns="http://pmd.sourceforge.net/ruleset/2.0.0" name="Exception throwing ruleset">
+    <description/>
+    <rule name="ExceptionThrowingRule"
+          language="java"
+          class="net.sourceforge.pmd.lang.rule.XPathRule">
+        <description>Use this rule to produce a processing error.</description>
+        <priority>3</priority>
+        <properties>
+            <property name="xpath">
+                <value><![CDATA[
+error()
+            ]]></value></property>
+        </properties>
+    </rule>
+</ruleset>
+

pmd-compat6/src/it/pmd-for-java/pom.xml

@@ -30,8 +30,12 @@
                 </executions>
                 <configuration>
                     <printFailingErrors>true</printFailingErrors>
-                    <skipPmdError>false</skipPmdError>
+                    <skipPmdError>true</skipPmdError> <!-- we want to capture processing errors -->
                     <minimumTokens>5</minimumTokens>
+                    <rulesets>
+                        <ruleset>/rulesets/java/maven-pmd-plugin-default.xml</ruleset>
+                        <ruleset>${project.basedir}/exception_ruleset.xml</ruleset>
+                    </rulesets>
                 </configuration>
                 <dependencies>
                     <dependency>

pmd-compat6/src/it/pmd-for-java/verify.bsh

@@ -51,3 +51,7 @@ String textReport = readFile(pmdTextReport);
 if (!textReport.contains(mainFile + ":5:\tUnusedLocalVariable")) {
     throw new RuntimeException("Expected violation has not been reported in TXT");
 }
+
+if (!pmdXml.contains("<error filename=\"" + mainFile.getAbsolutePath()) || !pmdXml.contains(mainFile + "\" msg=\"PmdXPathException")) {
+    throw new RuntimeException("Processing error has not been reported");
+}

pmd-compat6/src/main/java/net/sourceforge/pmd/Report.java

@@ -143,6 +143,11 @@ public final class Report {
         public Throwable getError() {
             return error;
         }
+
+        // ------------------- compat extensions --------------------
+        public String getFile() {
+            return file.getAbsolutePath();
+        }
     }
 
     /**