Merge ~newell-jensen/maas:lp1690781 into maas:master

[Newell Jensen]

LP: #1690781 -- virsh command returns an error string without raising an exception. Check returned string for error to try qemu emulator.

[Blake Rouse (blake-rouse)]

Looks good.

review: Approve

diff --git a/src/provisioningserver/drivers/pod/tests/test_virsh.py b/src/provisioningserver/drivers/pod/tests/test_virsh.py
index 8b32a48..18eb2d8 100644
--- a/src/provisioningserver/drivers/pod/tests/test_virsh.py
+++ b/src/provisioningserver/drivers/pod/tests/test_virsh.py
@@ -1776,7 +1776,7 @@ class TestVirshSSH(MAASTestCase):
     def test_get_domain_capabilities_for_qemu(self):
         conn = self.configure_virshssh('')
         self.patch(virsh.VirshSSH, "run").side_effect = [
-            factory.make_exception(),
+            'error: message from virsh',
             SAMPLE_CAPABILITY_QEMU,
         ]
         self.assertEqual({
diff --git a/src/provisioningserver/drivers/pod/virsh.py b/src/provisioningserver/drivers/pod/virsh.py
index 4d47632..9ca1f7a 100644
--- a/src/provisioningserver/drivers/pod/virsh.py
+++ b/src/provisioningserver/drivers/pod/virsh.py
@@ -1055,14 +1055,14 @@ class VirshSSH(pexpect.spawn):
 
         Determines the type and emulator of the domain to use.
         """
-        try:
-            # Test for KVM support first.
-            xml = self.run(['domcapabilities', '--virttype', 'kvm'])
-            emulator_type = 'kvm'
-        except Exception:
+        # Test for KVM support first.
+        xml = self.run(['domcapabilities', '--virttype', 'kvm'])
+        if xml.startswith('error'):
             # Fallback to qemu support. Fail if qemu not supported.
             xml = self.run(['domcapabilities', '--virttype', 'qemu'])
             emulator_type = 'qemu'
+        else:
+            emulator_type = 'kvm'
 
         # XXX newell 2017-05-18 bug=1690781
         # Check to see if the XML output was an error.