[PATCH] libbtrfsutil: fix unprivileged tests if kernel lacks support

[Omar Sandoval <osandov@xxxxxxxxxxx>]

From: Omar Sandoval <osandov@xxxxxx>

I apparently didn't test this on a pre-4.18 kernel.
test_subvolume_info_unprivileged() checks for an ENOTTY, but this
doesn't seem to work correctly with subTest().
test_subvolume_iterator_unprivileged() doesn't have a check at all. Add
an explicit check to both before doing the actual test.

Signed-off-by: Omar Sandoval <osandov@xxxxxx>
---
Based on the devel branch.

 libbtrfsutil/python/tests/test_subvolume.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libbtrfsutil/python/tests/test_subvolume.py b/libbtrfsutil/python/tests/test_subvolume.py
index 99ec97bc..b06a1d3d 100644
--- a/libbtrfsutil/python/tests/test_subvolume.py
+++ b/libbtrfsutil/python/tests/test_subvolume.py
@@ -168,12 +168,13 @@ class TestSubvolume(BtrfsTestCase):
 
         with drop_privs():
             try:
-                self._test_subvolume_info(subvol, snapshot)
+                btrfsutil.subvolume_info(self.mountpoint)
             except OSError as e:
                 if e.errno == errno.ENOTTY:
                     self.skipTest('BTRFS_IOC_GET_SUBVOL_INFO is not available')
                 else:
                     raise
+            self._test_subvolume_info(subvol, snapshot)
 
     def test_read_only(self):
         for arg in self.path_or_fd(self.mountpoint):
@@ -487,6 +488,13 @@ class TestSubvolume(BtrfsTestCase):
         try:
             os.chdir(self.mountpoint)
             with drop_privs():
+                try:
+                    list(btrfsutil.SubvolumeIterator('.'))
+                except OSError as e:
+                    if e.errno == errno.ENOTTY:
+                        self.skipTest('BTRFS_IOC_GET_SUBVOL_ROOTREF is not available')
+                    else:
+                        raise
                 self._test_subvolume_iterator()
         finally:
             os.chdir(pwd)
-- 
2.19.2