tiny-test-fw: only load module from the same file one time:

we should only load one module once.
if we load one module twice, python will regard the same object loaded in the first time and second time as different objects.
it will lead to strange errors like `isinstance(object, type_of_this_object)` return False

tools/tiny-test-fw/Utility/__init__.py

@@ -38,11 +38,23 @@ def console_log(data, color="white", end="\n"):
     sys.stdout.flush()
 
 
+__LOADED_MODULES = dict()
+# we should only load one module once.
+# if we load one module twice,
+# python will regard the same object loaded in the first time and second time as different objects.
+# it will lead to strange errors like `isinstance(object, type_of_this_object)` return False
+
+
 def load_source(name, path):
+    try:
+        return __LOADED_MODULES[name]
+    except KeyError:
         try:
             from importlib.machinery import SourceFileLoader
-        return SourceFileLoader(name, path).load_module()
+            ret = SourceFileLoader(name, path).load_module()
         except ImportError:
             # importlib.machinery doesn't exists in Python 2 so we will use imp (deprecated in Python 3)
             import imp
-        return imp.load_source(name, path)
+            ret = imp.load_source(name, path)
+        __LOADED_MODULES[name] = ret
+        return ret