selftests: Skip partitions test when mkfs not available

This test requires mkfs binary in order to run, while it's not really
essential for avocado testing. Let's skip it when it's not available.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

selftests/unit/test_utils_partition.py

@@ -26,6 +26,8 @@ class TestPartition(unittest.TestCase):
     Unit tests for avocado.utils.partition
     """
 
+    @unittest.skipIf(process.system("which mkfs", ignore_status=True),
+                     "mkfs is required for these tests to run.")
     def setUp(self):
         try:
             process.system("/bin/true", sudo=True)