Fix the svg tests on archlinux

tests/test_libmat2.py

@@ -445,7 +445,10 @@ class TestCleaning(unittest.TestCase):
             'meta': {
                 'WorkDescription': "This is a test svg image for mat2's testsuite",
             },
-            'expected_meta': {},
+            'expected_meta': {
+                'ImageSize': '128x128',
+                'Megapixels': '0.016',
+            },
         } ,{
             'name': 'ppm',
             'parser': images.PPMParser,
@@ -506,6 +509,7 @@ class TestCleaning(unittest.TestCase):
 
     def test_all_parametred(self):
         for case in self.data:
+            with self.subTest(case=case):
                 if 'ffmpeg' in case:
                     try:
                         video._get_ffmpeg_path()