Improve error message when protected project cannot be deleted

Change-Id: Ifea183aaba8df4642be89cbd04a4511cbaee1356
diff --git a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/projectconfig/ProjectConfigDeleteHandler.java b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/projectconfig/ProjectConfigDeleteHandler.java
index 9d4f760..2d6b0cc 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/deleteproject/projectconfig/ProjectConfigDeleteHandler.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/deleteproject/projectconfig/ProjectConfigDeleteHandler.java
@@ -18,7 +18,6 @@
 import com.google.common.base.Joiner;
 import com.google.common.collect.Iterables;
 import com.google.gerrit.extensions.common.ProjectInfo;
-import com.google.gerrit.server.config.SitePaths;
 import com.google.gerrit.server.project.ListChildProjects;
 import com.google.gerrit.server.project.ProjectResource;
 import com.google.inject.Inject;
@@ -30,15 +29,11 @@
 public class ProjectConfigDeleteHandler {
 
   private final ProtectedProjects protectedProjects;
-  private final SitePaths site;
   private final Provider<ListChildProjects> listChildProjectsProvider;
 
   @Inject
   public ProjectConfigDeleteHandler(
-      SitePaths site,
-      ProtectedProjects protectedProjects,
-      Provider<ListChildProjects> listChildProjectsProvider) {
-    this.site = site;
+      ProtectedProjects protectedProjects, Provider<ListChildProjects> listChildProjectsProvider) {
     this.protectedProjects = protectedProjects;
     this.listChildProjectsProvider = listChildProjectsProvider;
   }
@@ -50,7 +45,8 @@
 
   private void assertIsNotProtected(ProjectResource rsrc) throws CannotDeleteProjectException {
     if (protectedProjects.isProtected(rsrc)) {
-      throw new CannotDeleteProjectException("Perhaps you meant to rm -fR " + site.site_path);
+      throw new CannotDeleteProjectException(
+          "Cannot delete project because it is protected against deletion");
     }
   }