Block the reported user before destroying the record

This is intended to prevent the user from creating new objects while the
transaction that removes them is being run, resulting in objects with
nil authors which can then not be edited.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/7117

app/controllers/admin/abuse_reports_controller.rb

@@ -6,11 +6,9 @@ class Admin::AbuseReportsController < Admin::ApplicationController
   def destroy
     abuse_report = AbuseReport.find(params[:id])
-    if params[:remove_user]
-      abuse_report.user.destroy
-    end
-
+    abuse_report.remove_user if params[:remove_user]
     abuse_report.destroy
+
     render nothing: true
   end
 end

app/models/abuse_report.rb

@@ -19,6 +19,11 @@ class AbuseReport < ActiveRecord::Base
   validates :message, presence: true
   validates :user_id, uniqueness: true
+  def remove_user
+    user.block
+    user.destroy
+  end
+
   def notify
     return unless self.persisted?

spec/models/abuse_report_spec.rb

@@ -29,6 +29,22 @@ RSpec.describe AbuseReport, type: :model do
     it { is_expected.to validate_uniqueness_of(:user_id) }
   end
+  describe '#remove_user' do
+    it 'blocks the user' do
+      report = build(:abuse_report)
+
+      allow(report.user).to receive(:destroy)
+
+      expect { report.remove_user }.to change { report.user.blocked? }.to(true)
+    end
+
+    it 'removes the user' do
+      report = build(:abuse_report)
+
+      expect { report.remove_user }.to change { User.count }.by(-1)
+    end
+  end
+
   describe '#notify' do
     it 'delivers' do
       expect(AbuseReportMailer).to receive(:notify).with(subject.id).