translate copied links in longdesc attributes

closes #ADMIN-1409

Change-Id: I5291355cb21246a638e71003c70dc131f7f6e8e2
Reviewed-on: https://gerrit.instructure.com/163522
Tested-by: Jenkins
Reviewed-by: Mysti Sadler <mysti@instructure.com>
QA-Review: Mysti Sadler <mysti@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>

lib/imported_html_converter.rb

@@ -23,7 +23,7 @@ class ImportedHtmlConverter
   include HtmlTextHelper
 
   CONTAINER_TYPES = ['div', 'p', 'body']
-  LINK_ATTRS = ['rel', 'href', 'src', 'data', 'value']
+  LINK_ATTRS = ['rel', 'href', 'src', 'data', 'value', 'longdesc']
 
   attr_reader :link_parser, :link_resolver, :link_replacer
 

spec/models/content_migration/course_copy_spec.rb

@@ -608,6 +608,17 @@ describe ContentMigration do
       expect(@copy_to.reload.syllabus_body).to include "/courses/#{@copy_to.id}/files/#{att2.id}/download"
     end
 
+    it "should copy weird longdesc things" do
+      page = @copy_from.wiki_pages.create!(:title => "page")
+      @copy_from.syllabus_body = "<img longdesc=\"/courses/#{@copy_from.id}/pages/#{page.url}/>"
+      @copy_from.save!
+
+      run_course_copy
+
+      page2 = @copy_to.wiki_pages.where(:migration_id => mig_id(page)).first
+      expect(@copy_to.reload.syllabus_body).to include "/courses/#{@copy_to.id}/pages/#{page2.url}"
+    end
+
     it "should re-use kaltura media objects" do
       expect {
         media_id = '0_deadbeef'