[tests] Functional tests must explicitly set num_nodes

test/functional/proxy_test.py

@@ -42,6 +42,9 @@ from test_framework.netutil import test_ipv6_local
 RANGE_BEGIN = PORT_MIN + 2 * PORT_RANGE  # Start after p2p and rpc ports
 
 class ProxyTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 4
+
     def setup_nodes(self):
         self.have_ipv6 = test_ipv6_local()
         # Create two proxies on different ports