[tests] fix flake8 warnings in sendheaders.py

test/functional/sendheaders.py

@@ -83,16 +83,32 @@ d. Announce 49 headers that don't connect.
 e. Announce one more that doesn't connect.
    Expect: disconnect.
 """
-
-from test_framework.mininode import *
-from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import *
 from test_framework.blocktools import create_block, create_coinbase
+from test_framework.mininode import (
+    CBlockHeader,
+    CInv,
+    NODE_WITNESS,
+    NetworkThread,
+    NodeConnCB,
+    mininode_lock,
+    msg_block,
+    msg_getblocks,
+    msg_getdata,
+    msg_getheaders,
+    msg_headers,
+    msg_inv,
+    msg_sendheaders,
+)
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    sync_blocks,
+    wait_until,
+)
 
+DIRECT_FETCH_RESPONSE_TIME = 0.05
 
-direct_fetch_response_time = 0.05
-
-class TestNode(NodeConnCB):
+class BaseNode(NodeConnCB):
     def __init__(self):
         super().__init__()
         self.block_announced = False
@@ -136,8 +152,8 @@ class TestNode(NodeConnCB):
     # right header or the right inv
     # inv and headers should be lists of block hashes
     def check_last_announcement(self, headers=None, inv=None):
-        expect_headers = headers if headers != None else []
-        expect_inv = inv if inv != None else []
+        expect_headers = headers if headers is not None else []
+        expect_inv = inv if inv is not None else []
         test_function = lambda: self.block_announced
         wait_until(test_function, timeout=60, lock=mininode_lock)
         with mininode_lock:
@@ -217,10 +233,10 @@ class SendHeadersTest(BitcoinTestFramework):
 
     def run_test(self):
         # Setup the p2p connections and start up the network thread.
-        inv_node = self.nodes[0].add_p2p_connection(TestNode())
+        inv_node = self.nodes[0].add_p2p_connection(BaseNode())
         # Set nServices to 0 for test_node, so no block download will occur outside of
         # direct fetching
-        test_node = self.nodes[0].add_p2p_connection(TestNode(), services=NODE_WITNESS)
+        test_node = self.nodes[0].add_p2p_connection(BaseNode(), services=NODE_WITNESS)
 
         NetworkThread().start()  # Start up network handling in another thread
 
@@ -453,7 +469,7 @@ class SendHeadersTest(BitcoinTestFramework):
 
         test_node.send_header_for_blocks(blocks)
         test_node.sync_with_ping()
-        test_node.wait_for_getdata([x.sha256 for x in blocks], timeout=direct_fetch_response_time)
+        test_node.wait_for_getdata([x.sha256 for x in blocks], timeout=DIRECT_FETCH_RESPONSE_TIME)
 
         [test_node.send_message(msg_block(x)) for x in blocks]
 
@@ -484,13 +500,13 @@ class SendHeadersTest(BitcoinTestFramework):
         # both blocks (same work as tip)
         test_node.send_header_for_blocks(blocks[1:2])
         test_node.sync_with_ping()
-        test_node.wait_for_getdata([x.sha256 for x in blocks[0:2]], timeout=direct_fetch_response_time)
+        test_node.wait_for_getdata([x.sha256 for x in blocks[0:2]], timeout=DIRECT_FETCH_RESPONSE_TIME)
 
         # Announcing 16 more headers should trigger direct fetch for 14 more
         # blocks
         test_node.send_header_for_blocks(blocks[2:18])
         test_node.sync_with_ping()
-        test_node.wait_for_getdata([x.sha256 for x in blocks[2:16]], timeout=direct_fetch_response_time)
+        test_node.wait_for_getdata([x.sha256 for x in blocks[2:16]], timeout=DIRECT_FETCH_RESPONSE_TIME)
 
         # Announcing 1 more header should not trigger any response
         test_node.last_message.pop("getdata", None)