Fix exception re-raise during task execution for py34

This is the code fragment from six (executed when the interpreter is
python 3):

    def reraise(tp, value, tb=None):
        if value is None:
            value = tp()
        if value.__traceback__ is not tb:
            raise value.with_traceback(tb)
        raise value

We want `raise value` or `raise value.with_traceback(tb)` to be
executed as we are invoking six.reraise with a class instance.

Change-Id: Ic0c7e14cecb1cbdcb8cae87047e20514c4d38301

shade/task_manager.py

@@ -66,7 +66,8 @@ class Task(object):
     def wait(self):
         self._finished.wait()
         if self._exception:
-            six.reraise(self._exception, None, self._traceback)
+            six.reraise(type(self._exception), self._exception,
+                        self._traceback)
         return self._result
 
     def run(self, client):

shade/tests/unit/test_task_manager.py

@@ -0,0 +1,42 @@
+# Copyright (c) 2015 Hewlett-Packard Development Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from shade import task_manager
+from shade.tests.unit import base
+
+
+class TestException(Exception):
+    pass
+
+
+class TestTask(task_manager.Task):
+    def main(self, client):
+        raise TestException("This is a test exception")
+
+
+class TestTaskManager(base.TestCase):
+
+    def setUp(self):
+        super(TestTaskManager, self).setUp()
+        self.manager = task_manager.TaskManager(name='test', client=self)
+
+    def test_wait_re_raise(self):
+        """Test that Exceptions thrown in a Task is reraised correctly
+
+        This test is aimed to six.reraise(), called in Task::wait().
+        Specifically, we test if we get the same behaviour with all the
+        configured interpreters (e.g. py27, p34, pypy, ...)
+        """
+        self.assertRaises(TestException, self.manager.submitTask, TestTask())