Libguestfs - Mar 2016 - Malformed XML if LIBGUESTFS_HV is defined.

I was going to post this as a patch, but I realize the patch is just
working around an actual bug in the libvirt backend [not in libvirt].
Anyway, posting it here so we don't forget about it.

Rich.

This test fails under these conditions, for rather obscure reasons:

 - if LIBGUESTFS_HV is set, launch-libvirt.c:is_custom_hv returns true

 - this disables SELinux labelling in launch-libvirt.c

 - the test fails because the XML is malformed:

   XML error: label overrides require relabeling to be enabled at the domain
level

The XML is:

<?xml version="1.0"?>
<domain type="kvm"
xmlns:qemu="http://libvirt.org/schemas/domain/qemu/1.0">
...
  </os>
  <seclabel type="none"/>
...
  <devices>
   
<emulator>/home/rjones/d/qemu/x86_64-softmmu/qemu-system-x86_64</emulator>
...
    <disk device="disk" type="file">
      <source
file="/home/rjones/d/libguestfs/tmp/libguestfsgcFyFy/overlay1">
        <seclabel model="selinux" relabel="no"/>
      </source>
      <target dev="sda" bus="scsi"/>
      <driver name="qemu" type="qcow2"
cache="unsafe"/>
      <address type="drive" controller="0"
bus="0" target="0" unit="0"/>
    </disk>
...
---
 python/t/test820RHBZ912499.py | 1 +
 python/t/tests_helper.py      | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/python/t/test820RHBZ912499.py b/python/t/test820RHBZ912499.py
index ac381d0..1efed6b 100644
--- a/python/t/test820RHBZ912499.py
+++ b/python/t/test820RHBZ912499.py
@@ -31,6 +31,7 @@ from .tests_helper import *
 @skipUnlessArchMatches ("(i.86|x86_64)")   # If the architecture
doesn't support IDE, skip the test.
 @skipUnlessGuestfsBackendIs ('libvirt')
 @skipUnlessLibvirtHasCPointer ()
+@skipIfCustomHV ()
 class Test820RHBZ912499 (unittest.TestCase):
     def setUp (self):
         # Create a test disk.
diff --git a/python/t/tests_helper.py b/python/t/tests_helper.py
index c32e231..89acd93 100644
--- a/python/t/tests_helper.py
+++ b/python/t/tests_helper.py
@@ -18,6 +18,7 @@
 # Utilities for the tests of the Python bindings.
 
 import sys
+import os
 import unittest
 
 
@@ -68,3 +69,9 @@ def skipUnlessArchMatches (arch_re):
     if not rex.match (machine):
         return unittest.skip ("the current architecture (%s) does not
match '%s'" % (machine, arch_re))
     return lambda func: func
+
+
+def skipIfCustomHV ():
+    if "LIBGUESTFS_HV" in os.environ:
+        return unittest.skip ("$LIBGUESTFS_HV is set")
+    return lambda func: func
-- 
2.7.4