[tests] Don't subclass from object for Python 3

test/functional/test_framework/test_framework.py

@@ -43,7 +43,7 @@ TEST_EXIT_PASSED = 0
 TEST_EXIT_FAILED = 1
 TEST_EXIT_SKIPPED = 77
 
-class BitcoinTestFramework(object):
+class BitcoinTestFramework():
     """Base class for a bitcoin test script.
 
     Individual bitcoin test scripts should subclass this class and override the set_test_params() and run_test() methods.