[test] fix failure on python3

binary files shouldn't be opened in text mode

test/unittest_transforms.py

@@ -96,7 +96,7 @@ r2MAoIO1DSsuM23SzgmqubGJEZuSRWhR
                 self.skipTest('pdflatex not installed')
             else:
                 raise
-        data = TransformData(open(osp.join(DATAPATH, 'hello.pdf')).read(),
+        data = TransformData(open(osp.join(DATAPATH, 'hello.pdf'), 'rb').read(),
                              'application/pdf', 'utf8')
         converted = ENGINE.convert(data, 'text/plain').decode().strip()
         self.assertEqual(converted, u'hello')