added spec to ensure error messages are present

Author: Fivell

spec/import_spec.rb

@@ -312,6 +312,7 @@ def upload_file!(name, ext = 'csv')
           upload_file!(:authors_invalid_model)
           expect(page).to have_content 'Failed to import 1 author'
           expect(page).to have_content 'Successfully imported 1 author'
+          expect(page).to have_content 'Last name has already been taken - Doe'
           expect(Author.count).to eq(2)
         end