Fixup uses of mock in hyperv tests

I ended poking around a bit after mock 1.1.4.

The current skip is fixable by using a stateful side effect - the only
reason the test ever worked before is that mock 1.0.1 returned the
same data from every read call, which was explicitly fixed in Python
3.4.

However one of the other 'fixes' was buggy: it works by making the
strings match up but the code under test can be broken by not doing
the second open/read and it will still pass : thus the test is invalid
and should be skipped to avoid incorrect coverage stats.

Change-Id: Idec1b6b24e6d9d4a7567ae1f7753bffb9cb8bd5b
Closes-Bug: #1473401

nova/tests/unit/virt/hyperv/test_vhdutils.py

@@ -14,7 +14,6 @@
 
 import mock
 from oslo_utils import units
-import testtools
 
 from nova import test
 from nova.virt.hyperv import constants
@@ -243,12 +242,18 @@ class VHDUtilsTestCase(VHDUtilsBaseTestCase):
             self.assertEqual(constants.DISK_FORMAT_VHDX, format)
 
     def test_get_vhd_format_vhd(self):
-        raise testtools.TestCase.skipException("Bug 1473401")
         with mock.patch('nova.virt.hyperv.vhdutils.open',
-                        mock.mock_open(read_data=vhdutils.VHD_SIGNATURE),
+                        mock.mock_open(),
                         create=True) as mock_open:
             f = mock_open.return_value
             f.tell.return_value = 1024
+            readdata = ['notthesig', vhdutils.VHD_SIGNATURE]
+
+            def read(*args):
+                for content in readdata:
+                    yield content
+
+            f.read.side_effect = read()
 
             format = self._vhdutils.get_vhd_format(self._FAKE_VHD_PATH)
 

nova/tests/unit/virt/hyperv/test_vmops.py

@@ -19,6 +19,7 @@ import mock
 from oslo_concurrency import processutils
 from oslo_config import cfg
 from oslo_utils import units
+import unittest2
 
 from nova import exception
 from nova.tests.unit import fake_instance
@@ -965,6 +966,7 @@ class VMOpsTestCase(test_base.HyperVBaseTestCase):
             self._vmops._MAX_CONSOLE_LOG_FILE_SIZE)
         fake_iothread.return_value.start.assert_called_once_with()
 
+    @unittest2.skip('mock_open in 1.2 read only works once 1475661')
     @mock.patch("os.path.exists")
     def test_get_console_output(self, fake_path_exists):
         mock_instance = fake_instance.fake_instance_obj(self.context)
@@ -974,7 +976,7 @@ class VMOpsTestCase(test_base.HyperVBaseTestCase):
             mock.sentinel.FAKE_PATH, mock.sentinel.FAKE_PATH_ARCHIVED)
 
         with mock.patch('nova.virt.hyperv.vmops.open',
-                        mock.mock_open(read_data=self.FAKE_LOG * 2),
+                        mock.mock_open(read_data=self.FAKE_LOG),
                         create=True):
             instance_log = self._vmops.get_console_output(mock_instance)
             # get_vm_console_log_paths returns 2 paths.