python: Fix yaml.load warnings

Since pyyaml 5.1 yaml.load without specifing loader is deprecated
Details: https://msg.pyyaml.org/load

To keep code compatible with older versions of pyyaml
and keep best perfomance CLoader with fallback to Loader is used.

tools/tiny-test-fw/TestCase.py

@@ -14,6 +14,11 @@
 
 import yaml
 
+try:
+    from yaml import CLoader as Loader
+except ImportError:
+    from yaml import Loader as Loader
+
 
 class TestCase(object):
     """
@@ -45,7 +50,7 @@ class TestCase(object):
         """
         doc_string = self.test_method.__doc__
         try:
-            doc = yaml.load(doc_string)
+            doc = yaml.load(doc_string, Loader=Loader)
         except (AttributeError, OSError, UnicodeDecodeError):
             doc = self.DEFAULT_CASE_DOC
         doc.update(self.test_method.env_args)