Code review: throw exception with cause

In order to be able to do that at all, I had to add a constructor taking
a throwable first. Now, even though a cause is propagated, at the time
of writing this Maven Compiler will just catch the
NoSuchCompilerException we throw, ignore its message and root cause and
throw a new MojoExecutionException instead. :-/

Relates to codehaus-plexus#347.

plexus-compiler-manager/src/main/java/org/codehaus/plexus/compiler/manager/DefaultCompilerManager.java

@@ -69,7 +69,7 @@ public Compiler getCompiler(String compilerId) throws NoSuchCompilerException {
         } catch (Exception e) {
             // DI could not construct compiler
             log.error(ERROR_MESSAGE, compilerId);
-            throw new NoSuchCompilerException(compilerId);
+            throw new NoSuchCompilerException(compilerId, e);
         }
     }
 }

plexus-compiler-manager/src/main/java/org/codehaus/plexus/compiler/manager/NoSuchCompilerException.java

@@ -31,8 +31,11 @@ public class NoSuchCompilerException extends Exception {
     private final String compilerId;
 
     public NoSuchCompilerException(String compilerId) {
-        super("No such compiler '" + compilerId + "'.");
+        this(compilerId, null);
+    }
 
+    public NoSuchCompilerException(String compilerId, Throwable cause) {
+        super("No such compiler '" + compilerId + "'", cause);
         this.compilerId = compilerId;
     }