fix error handling

master/buildbot/libvirtbuildslave.py

@@ -253,9 +253,10 @@ def start_instance(self, build):
             else:
                 self.domain = yield self.connection.lookupByName(self.name)
                 yield self.domain.create()
-        except Exception:
-            log.msg("Cannot start a VM (%s), failing gracefully and triggering a new build check" % self.name)
-            log.err(failure.Failure())
+        except:
+            log.err(failure.Failure(),
+                    "Cannot start a VM (%s), failing gracefully and triggering"
+                    "a new build check" % self.name)
             self.domain = None
             defer.returnValue(False)
 

master/buildbot/test/unit/test_libvirtslave.py

@@ -19,6 +19,7 @@
 from twisted.python import failure
 from buildbot import libvirtbuildslave, config
 from buildbot.test.fake import libvirt
+from buildbot.test.util import compat
 
 
 class TestLibVirtSlave(unittest.TestCase):
@@ -107,6 +108,28 @@ def test_start_instance(self):
 
         self.assertEqual(started, True)
 
+    @compat.usesFlushLoggedErrors
+    @defer.inlineCallbacks
+    def test_start_instance_create_fails(self):
+        bs = self.ConcreteBuildSlave('b', 'p', self.conn, 'p', 'o',
+            xml='<xml/>')
+
+        prep = mock.Mock()
+        prep.side_effect = lambda: defer.succeed(0)
+        self.patch(bs, "_prepare_base_image", prep)
+
+        create = mock.Mock()
+        create.side_effect = lambda self : defer.fail(
+                failure.Failure(RuntimeError('oh noes')))
+        self.patch(libvirtbuildslave.Connection, 'create', create)
+
+        yield bs._find_existing_deferred
+        started = yield bs.start_instance(mock.Mock())
+
+        self.assertEqual(bs.domain, None)
+        self.assertEqual(started, False)
+        self.assertEqual(len(self.flushLoggedErrors(RuntimeError)), 1)
+
     @defer.inlineCallbacks
     def setup_canStartBuild(self):
         bs = self.ConcreteBuildSlave('b', 'p', self.conn, 'p', 'o')