Fix missing argument to QemuImageInfo

set the default value for cmd_output to None. _parse
does work fine with None or empty string

Fixes LP# 1157412

Change-Id: Ib63f2fd227633b96db613ce29563d1929536819a

nova/tests/virt/test_images.py

@@ -0,0 +1,24 @@
+#    Copyright 2013 IBM Corp.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+from nova import test
+from nova.virt import images
+
+
+class QemuTestCase(test.TestCase):
+    def test_qemu_info_with_bad_path(self):
+        image_info = images.qemu_img_info("/path/that/does/not/exist")
+        self.assertTrue(image_info)
+        self.assertTrue(str(image_info))

nova/virt/images.py

@@ -49,7 +49,7 @@ class QemuImgInfo(object):
     TOP_LEVEL_RE = re.compile(r"^([\w\d\s\_\-]+):(.*)$")
     SIZE_RE = re.compile(r"\(\s*(\d+)\s+bytes\s*\)", re.I)
 
-    def __init__(self, cmd_output):
+    def __init__(self, cmd_output=None):
         details = self._parse(cmd_output)
         self.image = details.get('image')
         self.backing_file = details.get('backing_file')