Port scheduler host manager to Python 3

* Rewrite ReadOnlyDict using collections.Mapping: collections.Mapping
  has no method to modify the dictionary and is available on Python 2
  and Python 3. Add also a __repr__() method to ease debug. Remove
  ReadOnlyDict.update() method: a read-only dictionary must not be
  modifiable.
* test_host_manager.py: sort dictionaries using a key function to
  have a reliable order for the list of dictionaries. On Python 3,
  the hash function is now randomized.
* tox.ini. add cinder/tests/unit/scheduler/ tests to Python 3.4

Blueprint cinder-python3
Change-Id: I34d98d6a75fef907251719f0d46b025d8e8b2b65

cinder/scheduler/host_manager.py

@@ -17,7 +17,7 @@
 Manage hosts in the current zone.
 """
 
-import UserDict
+import collections
 
 from oslo_config import cfg
 from oslo_log import log as logging
@@ -57,36 +57,25 @@ CONF.import_opt('max_over_subscription_ratio', 'cinder.volume.driver')
 LOG = logging.getLogger(__name__)
 
 
-class ReadOnlyDict(UserDict.IterableUserDict):
+class ReadOnlyDict(collections.Mapping):
     """A read-only dict."""
     def __init__(self, source=None):
-        self.data = {}
-        self.update(source)
-
-    def __setitem__(self, key, item):
-        raise TypeError
-
-    def __delitem__(self, key):
-        raise TypeError
-
-    def clear(self):
-        raise TypeError
-
-    def pop(self, key, *args):
-        raise TypeError
-
-    def popitem(self):
-        raise TypeError
-
-    def update(self, source=None):
-        if source is None:
-            return
-        elif isinstance(source, UserDict.UserDict):
-            self.data = source.data
-        elif isinstance(source, type({})):
-            self.data = source
+        if source is not None:
+            self.data = dict(source)
         else:
-            raise TypeError
+            self.data = {}
+
+    def __getitem__(self, key):
+        return self.data[key]
+
+    def __iter__(self):
+        return iter(self.data)
+
+    def __len__(self):
+        return len(self.data)
+
+    def __repr__(self):
+        return '%s(%r)' % (self.__class__.__name__, self.data)
 
 
 class HostState(object):

cinder/tests/unit/scheduler/test_host_manager.py

@@ -389,8 +389,13 @@ class HostManagerTestCase(test.TestCase):
                         'provisioned_capacity_gb': 9300},
                 }
             ]
+
+            def sort_func(data):
+                return data['name']
+
             self.assertEqual(len(expected), len(res))
-            self.assertEqual(sorted(expected), sorted(res))
+            self.assertEqual(sorted(expected, key=sort_func),
+                             sorted(res, key=sort_func))
 
 
 class HostStateTestCase(test.TestCase):

tox.ini

@@ -31,6 +31,17 @@ commands =
   python -m testtools.run \
     cinder.tests.unit.image.test_glance \
     cinder.tests.unit.keymgr.test_mock_key_mgr \
+    cinder.tests.unit.scheduler.test_allocated_capacity_weigher \
+    cinder.tests.unit.scheduler.test_capacity_weigher \
+    cinder.tests.unit.scheduler.test_chance_weigher \
+    cinder.tests.unit.scheduler.test_filter_scheduler \
+    cinder.tests.unit.scheduler.test_goodness_weigher \
+    cinder.tests.unit.scheduler.test_host_filters \
+    cinder.tests.unit.scheduler.test_host_manager \
+    cinder.tests.unit.scheduler.test_rpcapi \
+    cinder.tests.unit.scheduler.test_scheduler \
+    cinder.tests.unit.scheduler.test_scheduler_options \
+    cinder.tests.unit.scheduler.test_volume_number_weigher \
     cinder.tests.unit.targets.test_base_iscsi_driver \
     cinder.tests.unit.targets.test_cxt_driver \
     cinder.tests.unit.targets.test_iser_driver \