tests: Use explicit imports

test/functional/rpc_psbt.py

@@ -6,7 +6,10 @@
 """
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import *
+from test_framework.util import assert_equal, assert_raises_rpc_error, find_output
+
+import json
+import os
 
 # Create one-input, one-output, no-fee transaction:
 class PSBTTest(BitcoinTestFramework):