Fix test for svg2pdf preprocessor

IPython/nbconvert/preprocessors/tests/test_svg2pdf.py

@@ -42,7 +42,9 b' class Testsvg2pdf(PreprocessorTestsBase):'
         """Build a reveal slides notebook in memory for use with tests.
         Overrides base in PreprocessorTestsBase"""
 
-        outputs = [nbformat.new_output(output_type="image/svg+xml", output_svg=self.simple_svg)]
+        outputs = [nbformat.new_output(output_type='display_data',
+                                       data={'image/svg+xml':self.simple_svg})
+                  ]
         
         slide_metadata = {'slideshow' : {'slide_type': 'slide'}}
         subslide_metadata = {'slideshow' : {'slide_type': 'subslide'}}
@@ -71,4 +73,4 b' class Testsvg2pdf(PreprocessorTestsBase):'
         res = self.build_resources()
         preprocessor = self.build_preprocessor()
         nb, res = preprocessor(nb, res)
-        self.assertIn('application/pdf', nb.cells[0].outputs[0])
+        self.assertIn('application/pdf', nb.cells[0].outputs[0].data)