tests/object_dict.py: Add test for obj.__dict__ .

tests/basics/object_dict.py

+import sys
+
+class Foo:
+
+    def __init__(self):
+        self.a = 1
+        self.b = "bar"
+
+o = Foo()
+if not hasattr(o, "__dict__"):
+    print("SKIP")
+    sys.exit()
+
+print(o.__dict__ == {'a': 1, 'b': 'bar'})