Fix error when deleting a user who has projects

Closes #1856
Closes https://github.com/gitlabhq/gitlabhq/issues/9394

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.13.0 (unreleased)
+  - Fix error when deleting a user who has projects (Stan Hu)
   - Update maintenance documentation to explain no need to recompile asssets for omnibus installations (Stan Hu)
   - Support commenting on diffs in side-by-side mode (Stan Hu)
   - Fix JavaScript error when clicking on the comment button on a diff line that has a comment already (Stan Hu)

app/controllers/admin/users_controller.rb

@@ -86,7 +86,7 @@ class Admin::UsersController < Admin::ApplicationController
   end
 
   def destroy
-    DeleteUserService.new.execute(user)
+    DeleteUserService.new(current_user).execute(user)
 
     respond_to do |format|
       format.html { redirect_to admin_users_path }

app/controllers/registrations_controller.rb

@@ -6,7 +6,7 @@ class RegistrationsController < Devise::RegistrationsController
   end
 
   def destroy
-    DeleteUserService.new.execute(current_user)
+    DeleteUserService.new(current_user).execute(current_user)
 
     respond_to do |format|
       format.html { redirect_to new_user_session_path, notice: "Account successfully removed." }

app/services/delete_user_service.rb

 class DeleteUserService
+  attr_accessor :current_user
+
+  def initialize(current_user)
+    @current_user = current_user
+  end
+
   def execute(user)
     if user.solo_owned_groups.present?
       user.errors[:base] << 'You must transfer ownership or delete groups before you can remove user'

lib/api/users.rb

@@ -194,7 +194,7 @@ module API
         user = User.find_by(id: params[:id])
 
         if user
-          DeleteUserService.new.execute(user)
+          DeleteUserService.new(current_user).execute(user)
         else
           not_found!('User')
         end

spec/controllers/admin/users_controller_spec.rb

+require 'spec_helper'
+
+describe Admin::UsersController do
+  let(:admin)    { create(:admin) }
+
+  before do
+    sign_in(admin)
+  end
+
+  describe 'DELETE #user with projects' do
+    let(:user) { create(:user) }
+    let(:project) { create(:project, namespace: user.namespace) }
+
+    before do
+      project.team << [user, :developer]
+    end
+
+    it 'deletes user' do
+      delete :destroy, id: user.username, format: :json
+      expect(response.status).to eq(200)
+      expect { User.find(user.id) }.to raise_exception(ActiveRecord::RecordNotFound)
+    end
+  end
+end