rehome used neutron.tests.tools

This patch rehomes the OpenFixture class and reset_random_seed function
both which are from neutron.tests.tools as they are used by consumers
today [1].

[1] http://codesearch.openstack.org/?q=from%20neutron.tests%20import%20tools

Change-Id: I3d13a747f31e39c11f42e2f543eae3823cfbe356

neutron_lib/fixture.py

@@ -286,3 +286,25 @@ class DBResourceExtendFixture(fixtures.Fixture):
 
     def _restore(self):
         resource_extend._resource_extend_functions = self._backup
+
+
+class OpenFixture(fixtures.Fixture):
+    """Mock access to a specific file while preserving open for others."""
+
+    def __init__(self, filepath, contents=''):
+        self.path = filepath
+        self.contents = contents
+
+    def _setUp(self):
+        self.mock_open = mock.mock_open(read_data=self.contents)
+        self._orig_open = open
+
+        def replacement_open(name, *args, **kwargs):
+            if name == self.path:
+                return self.mock_open(name, *args, **kwargs)
+            return self._orig_open(name, *args, **kwargs)
+
+        self._patch = mock.patch('six.moves.builtins.open',
+                                 new=replacement_open)
+        self._patch.start()
+        self.addCleanup(self._patch.stop)

neutron_lib/tests/tools.py

@@ -13,8 +13,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import os
 import platform
 import random
+import time
 import warnings
 
 import fixtures
@@ -66,3 +68,13 @@ def get_random_cidr(version=4):
                                   random.randint(3, 254),
                                   24)
     return '2001:db8:%x::/%d' % (random.getrandbits(16), 64)
+
+
+def reset_random_seed():
+    # reset random seed to make sure other processes extracting values from RNG
+    # don't get the same results (useful especially when you then use the
+    # random values to allocate system resources from global pool, like ports
+    # to listen). Use both current time and pid to make sure no tests started
+    # at the same time get the same values from RNG
+    seed = time.time() + os.getpid()
+    random.seed(seed)

releasenotes/notes/rehome-testools-6fba053249e14d42.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - The ``OpenFixture`` class is now available in ``neutron_lib.fixtures``.
+  - The ``reset_random_seed`` function is now available in
+    ``neutron_lib.tests.tools``.