Fixed multiple py34 gate issues

1. Scope mock of 'open' to module

By mocking 'open' at the module level, we can avoid affecting
'open' calls from other modules.

2. Stop using LOG.exception in contexts with no sys.exc_info set

Python 3.4 logger fills in record.exc_info with sys.exc_info() result
[1], and then it uses it to determine the current exception [2] to
append to the log message. Since there is no exception, exc_info[1] is
None, and we get AttributeError inside traceback module.

It's actually a bug in Python interpreter that it attempt to access the
attribute when there is no exception. It turns out that it's fixed in
latest master of cPython [3] (the intent of the patch does not seem
relevant, but it removes the offending code while reshuffling the code).
Note that now cPython correctly checks the exception value before
accessing its attributes [4].

The patch in cPython that resulted in the failure is [5] and is present
since initial Python 3k releases.

The patch in fixtures that broke us is [6].

[1]: https://hg.python.org/cpython/file/tip/Lib/logging/__init__.py#l1412
[2]: https://hg.python.org/cpython/file/tip/Lib/logging/__init__.py#l575
[3]: https://hg.python.org/cpython/rev/73afda5a4e4c
[4]: https://hg.python.org/cpython/rev/73afda5a4e4c#l6.484
[5]: https://hg.python.org/cpython/rev/2ee09afee126
[6]: 67dd295694

Closes-Bug: #1503847
Closes-Bug: #1504053
Co-Authored-By: Ihar Hrachyshka <ihrachys@redhat.com>
Change-Id: I456b7846b8a53e4d3f8c91583685e0e1eaa84719

neutron/manager.py

@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import sys
 import weakref
 
 from oslo_config import cfg
@@ -136,19 +137,22 @@ class NeutronManager(object):
     @staticmethod
     def load_class_for_provider(namespace, plugin_provider):
         if not plugin_provider:
-            LOG.exception(_LE("Error, plugin is not set"))
+            LOG.error(_LE("Error, plugin is not set"))
             raise ImportError(_("Plugin not found."))
         try:
             # Try to resolve plugin by name
             mgr = driver.DriverManager(namespace, plugin_provider)
             plugin_class = mgr.driver
-        except RuntimeError as e1:
+        except RuntimeError:
+            e1_info = sys.exc_info()
             # fallback to class name
             try:
                 plugin_class = importutils.import_class(plugin_provider)
-            except ImportError as e2:
-                LOG.exception(_LE("Error loading plugin by name, %s"), e1)
-                LOG.exception(_LE("Error loading plugin by class, %s"), e2)
+            except ImportError:
+                LOG.error(_LE("Error loading plugin by name"),
+                          exc_info=e1_info)
+                LOG.error(_LE("Error loading plugin by class"),
+                          exc_info=True)
                 raise ImportError(_("Plugin not found."))
         return plugin_class
 

neutron/policy.py

@@ -226,7 +226,7 @@ class OwnerCheck(policy.Check):
                 # If we are here split failed with both separators
                 err_reason = (_("Unable to find resource name in %s") %
                               self.target_field)
-                LOG.exception(err_reason)
+                LOG.error(err_reason)
                 raise exceptions.PolicyCheckError(
                     policy="%s:%s" % (self.kind, self.match),
                     reason=err_reason)
@@ -236,7 +236,7 @@ class OwnerCheck(policy.Check):
                 err_reason = (_("Unable to verify match:%(match)s as the "
                                 "parent resource: %(res)s was not found") %
                               {'match': self.match, 'res': parent_res})
-                LOG.exception(err_reason)
+                LOG.error(err_reason)
                 raise exceptions.PolicyCheckError(
                     policy="%s:%s" % (self.kind, self.match),
                     reason=err_reason)

neutron/services/provider_configuration.py

@@ -197,7 +197,7 @@ class ProviderConfiguration(object):
             if v['driver'] == driver:
                 msg = (_("Driver %s is not unique across providers") %
                        driver)
-                LOG.exception(msg)
+                LOG.error(msg)
                 raise n_exc.Invalid(msg)
 
     def _ensure_default_unique(self, type, default):
@@ -207,7 +207,7 @@ class ProviderConfiguration(object):
             if k[0] == type and v['default']:
                 msg = _("Multiple default providers "
                         "for service %s") % type
-                LOG.exception(msg)
+                LOG.error(msg)
                 raise n_exc.Invalid(msg)
 
     def add_provider(self, provider):

neutron/tests/unit/db/test_migration.py

@@ -341,7 +341,7 @@ class TestCli(base.BaseTestCase):
                 mock.patch.object(cli, '_use_separate_migration_branches',
                                   return_value=not branchless):
             fc.return_value.get_heads.return_value = heads
-            with mock.patch('six.moves.builtins.open') as mock_open:
+            with mock.patch.object(cli, 'open') as mock_open:
                 mock_open.return_value.__enter__ = lambda s: s
                 mock_open.return_value.__exit__ = mock.Mock()
                 mock_open.return_value.read.return_value = (