improve exception about missing rasterizer

Author: nidi3

graphviz-java/src/main/java/guru/nidi/graphviz/engine/Graphviz.java

@@ -226,8 +226,9 @@ public Graphviz filter(GraphvizFilter filter) {
 
     public Renderer rasterize(@Nullable Rasterizer rasterizer) {
         if (rasterizer == null) {
-            throw new IllegalArgumentException("The provided rasterizer implementation was not found. "
-                    + "Make sure that the batik-rasterizer or svg-salamander jar is available on the classpath.");
+            throw new IllegalArgumentException("The provided rasterizer implementation was not found."
+                    + " Make sure that either 'guru.nidi.com.kitfox:svgSalamander' or"
+                    + " 'org.apache.xmlgraphics:batik-rasterizer' is available on the classpath.");
         }
         final Options opts = options.format(rasterizer.format());
         final Graphviz graphviz = new Graphviz(graph, src, rasterizer, processOptions, opts, filters);

graphviz-java/src/main/java/guru/nidi/graphviz/engine/Renderer.java

@@ -112,7 +112,8 @@ private BufferedImage toImage(EngineResult result) {
     private BufferedImage toImage(String content) {
         if (graphviz.rasterizer == null) {
             throw new IllegalStateException("- Rasterizer explicitly set no null or\n"
-                    + "- neither Batik nor Salamander found on classpath.");
+                    + "- neither 'guru.nidi.com.kitfox:svgSalamander' nor 'org.apache.xmlgraphics:batik-rasterizer'"
+                    + " found on classpath.");
         }
         return graphviz.rasterizer.rasterize(graphviz, graphicsConfigurer, content);
     }