code: static MojoExecutionException unwrapTaskException(
              final Exception exception,
              @Nullable final Throwable cause) {
          if (cause instanceof CompletionException || cause instanceof ExecutionException) {
              return unwrapTaskException((Exception) cause, cause.getCause());
          } else if (cause != null) {
              return new MojoExecutionException("Class processing failed", cause);
          } else {
              return new MojoExecutionException("Unknown class processing exception", exception);
          }
      }
docs: /* package private