Add test for rpcpassword hash error

test/functional/feature_config_args.py

@@ -29,6 +29,10 @@ class ConfArgsTest(BitcoinTestFramework):
             conf.write('nono\n')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error reading configuration file: parse error on line 1: nono, if you intended to specify a negated option, use nono=1 instead')
 
+        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+            conf.write('server=1\nrpcuser=someuser\nrpcpassword=some#pass')
+        self.nodes[0].assert_start_raises_init_error(expected_msg='Error reading configuration file: parse error on line 3, using # in rpcpassword can be ambiguous and should be avoided')
+
         with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
             conf.write('')  # clear