vnf_generic: convert sshmanager to class

@contextmanager have an issue with respect to exceptions that makes
them not suitable for real usage.

@contextmanager uses yield to create a generator and then uses
generator.throw() to raise any exceptions.  Exceptions thrown from
generators loose their call stack due to the way generators work, so any
exception inside a context manager is harder to debug. For this reason
we don't use @contextmanager and instead always define a new class with
__enter__ and __exit__.

There is sample code that demonstrates the
issue with @contextmanager and generator.throw() here
https://gist.github.com/rbbratta/e28b6e64a4551522c3ac9815ca7f25f0

Change-Id: I5383c01f40a63e33680112f39b5bd9c858e328f1
Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/unit/benchmark/scenarios/networking/test_vnf_generic.py b/tests/unit/benchmark/scenarios/networking/test_vnf_generic.py
index 0d9fbafc5..9b7174e7e 100644
--- a/tests/unit/benchmark/scenarios/networking/test_vnf_generic.py
+++ b/tests/unit/benchmark/scenarios/networking/test_vnf_generic.py
@@ -23,7 +23,7 @@ import mock
 import os
 
 from yardstick.benchmark.scenarios.networking.vnf_generic import \
-    ssh_manager, NetworkServiceTestCase, IncorrectConfig, IncorrectSetup
+    SshManager, NetworkServiceTestCase, IncorrectConfig, IncorrectSetup
 from yardstick.network_services.collector.subscriber import Collector
 from yardstick.network_services.vnf_generic.vnf.base import \
     GenericTrafficGen, GenericVNF
@@ -304,7 +304,7 @@ class TestNetworkServiceTestCase(unittest.TestCase):
                 mock.Mock(return_value=(0, SYS_CLASS_NET+IP_ADDR_SHOW, ""))
             ssh.return_value = ssh_mock
             for node, node_dict in self.context_cfg["nodes"].items():
-                with ssh_manager(node_dict) as conn:
+                with SshManager(node_dict) as conn:
                     self.assertIsNotNone(conn)
 
     def test___init__(self):