iso: Extract volume id with xorriso if available

Pungi can use either genisoimage or xorriso to create ISOs.

It also needed isoinfo utility for querying volume ID from the ISO
image. However, the utility is part of the genisoimage suite of tools.

On systems that no longer provide genisoimage, the image would be
successfully generate with xorriso, but then pungi would fail to extract
the volume id leading to metadata with missing values.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/test_iso_wrapper.py

@@ -24,6 +24,19 @@ Supported ISO: no
 
 INCORRECT_OUTPUT = """This should never happen: File not found"""
 
+XORRISO_LOAD_OUTPUT = """\
+xorriso 1.5.4 : RockRidge filesystem manipulator, libburnia project.
+
+xorriso : NOTE : Loading ISO image tree from LBA 0
+xorriso : UPDATE :    7074 nodes read in 1 seconds
+Drive current: -indev 'dummy.iso'
+Media current: stdio file, overwriteable
+Media status : is written , is appendable
+Boot record  : El Torito , MBR isohybrid cyl-align-off GPT
+Media summary: 1 session, 5415454 data blocks, 10.3g data, 4086g free
+Volume id    : 'My volume id'
+"""
+
 # Cached to use in tests that mock os.listdir
 orig_listdir = os.listdir
 
@@ -187,6 +200,11 @@ class TestIsoUtils(unittest.TestCase):
         self.assertEqual(len(mock_unmount.call_args_list), 0)
         self.assertEqual(len(log.mock_calls), 1)
 
+    @mock.patch("pungi.wrappers.iso.run")
+    def test_get_volume_id_xorriso(self, mock_run):
+        mock_run.return_value = (0, XORRISO_LOAD_OUTPUT)
+        self.assertEqual(iso.get_volume_id("/dummy.iso", True), "My volume id")
+
 
 class TestCmpGraftPoints(unittest.TestCase):
     def assertSorted(self, *args):