Intermittent test failures in sendheaders.py #7246

MiniNode: Connecting to Bitcoin Node IP # 127.0.0.1:11106
MiniNode: Connecting to Bitcoin Node IP # 127.0.0.1:11106
Part 1: headers don't start before sendheaders message...
Part 1: success!
Part 2: announce blocks with headers after sendheaders message...
Part 2: success!
Part 3: headers announcements can stop after large reorg, and resume after headers/inv from peer...
Assertion failed: False != True
  File "/home/travis/build/bitcoin/bitcoin/bitcoin-i686-pc-linux-gnu/qa/rpc-tests/test_framework/test_framework.py", line 135, in main
    self.run_test()
  File "/home/travis/build/bitcoin/bitcoin/bitcoin-i686-pc-linux-gnu/qa/rpc-tests/sendheaders.py", line 426, in run_test
    assert_equal(test_node.check_last_announcement(headers=[tip]), True)
  File "/home/travis/build/bitcoin/bitcoin/bitcoin-i686-pc-linux-gnu/qa/rpc-tests/test_framework/util.py", line 394, in assert_equal
    raise AssertionError("%s != %s"%(str(thing1),str(thing2)))
Stopping nodes
Cleaning up
Failed

See e.g. https://travis-ci.org/bitcoin/bitcoin/jobs/98312801

Oops, I think I see the bug, though I'm not able to test my guess or submit a fix right now.

Before this block of code starting at line 423, I think we need to call clear_last_announcement on inv_node and test_node, or else there's a race condition.

            # New blocks should now be announced with header
            tip = self.mine_blocks(1)
            assert_equal(inv_node.check_last_announcement(inv=[tip]), True)
            assert_equal(test_node.check_last_announcement(headers=[tip]), True)