VTL: VppTestResult: Must implement empty constructor.

Subclasses of (unittest.TestResult|unittest.TextTestResult) must implement an empty constructor.

The standard python library unittests depend on the empty constructor.

Change-Id: I6d1bd2e7d6996d85a9da66cb7d40af0ed3c30e2b
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/test/framework.py b/test/framework.py
index 9d85be7..2a2dfd4 100644
--- a/test/framework.py
+++ b/test/framework.py
@@ -1034,7 +1034,8 @@
     core_crash_test_cases_info = set()
     current_test_case_info = None
 
-    def __init__(self, stream, descriptions, verbosity, runner):
+    def __init__(self, stream=None, descriptions=None, verbosity=None,
+                 runner=None):
         """
         :param stream File descriptor to store where to report test results.
             Set to the standard error stream by default.