[tests] Allow stderr to be tested against specified string

Allow bitcoind's stderr to be tested against a specified string on
shutdown.

test/functional/feature_includeconf.py

@@ -15,9 +15,8 @@ Verify that:
    file.
 """
 import os
-import tempfile
 
-from test_framework.test_framework import BitcoinTestFramework, assert_equal
+from test_framework.test_framework import BitcoinTestFramework
 
 class IncludeConfTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -44,20 +43,18 @@ class IncludeConfTest(BitcoinTestFramework):
 
         self.log.info("-includeconf cannot be used as command-line arg. subversion should still end with 'main; relative)/'")
         self.stop_node(0)
-        with tempfile.SpooledTemporaryFile(max_size=2**16) as log_stderr:
-            self.start_node(0, extra_args=["-includeconf=relative2.conf"], stderr=log_stderr)
 
-            subversion = self.nodes[0].getnetworkinfo()["subversion"]
-            assert subversion.endswith("main; relative)/")
-            log_stderr.seek(0)
-            stderr = log_stderr.read().decode('utf-8').strip()
-            assert_equal(stderr, 'warning: -includeconf cannot be used from commandline; ignoring -includeconf=relative2.conf')
+        self.start_node(0, extra_args=["-includeconf=relative2.conf"])
+
+        subversion = self.nodes[0].getnetworkinfo()["subversion"]
+        assert subversion.endswith("main; relative)/")
+        self.stop_node(0, expected_stderr="warning: -includeconf cannot be used from commandline; ignoring -includeconf=relative2.conf")
 
         self.log.info("-includeconf cannot be used recursively. subversion should end with 'main; relative)/'")
         with open(os.path.join(self.options.tmpdir, "node0", "relative.conf"), "a", encoding="utf8") as f:
             f.write("includeconf=relative2.conf\n")
 
-        self.restart_node(0)
+        self.start_node(0)
 
         subversion = self.nodes[0].getnetworkinfo()["subversion"]
         assert subversion.endswith("main; relative)/")

test/functional/test_framework/test_framework.py

@@ -289,9 +289,9 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
             for node in self.nodes:
                 coverage.write_all_rpc_commands(self.options.coveragedir, node.rpc)
 
-    def stop_node(self, i):
+    def stop_node(self, i, expected_stderr=''):
         """Stop a bitcoind test node"""
-        self.nodes[i].stop_node()
+        self.nodes[i].stop_node(expected_stderr)
         self.nodes[i].wait_until_stopped()
 
     def stop_nodes(self):

test/functional/test_framework/test_node.py

@@ -188,7 +188,7 @@ class TestNode():
             wallet_path = "wallet/%s" % wallet_name
             return self.rpc / wallet_path
 
-    def stop_node(self):
+    def stop_node(self, expected_stderr=''):
         """Stop the node."""
         if not self.running:
             return
@@ -197,6 +197,13 @@ class TestNode():
             self.stop()
         except http.client.CannotSendRequest:
             self.log.exception("Unable to stop node.")
+
+        # Check that stderr is as expected
+        self.stderr.seek(0)
+        stderr = self.stderr.read().decode('utf-8').strip()
+        if stderr != expected_stderr:
+            raise AssertionError("Unexpected stderr {} != {}".format(stderr, expected_stderr))
+
         del self.p2ps[:]
 
     def is_node_stopped(self):