Merge bitcoin/bitcoin#31746: test: Added coverage to the waitfornewbl…

…ock rpc

93747d9 test: Added coverage to the waitfornewblock rpc (kevkevinpal)

Pull request description:

  Added a test for the Negative timeout error if the rpc is given a negative value for its timeout arg

  This adds coverage to the `waitfornewblock` rpc

  you can check to see there is no coverage for this error by doing
  `grep -nri "Negative timeout" ./test/`

  and nothing shows up, you can also see by manually checking where we call `waitfornewblock` in the functional tests

ACKs for top commit:
  Sjors:
    tACK 93747d9
  achow101:
    ACK 93747d9
  brunoerg:
    code review ACK 93747d9
  tdb3:
    ACK 93747d9

Tree-SHA512: 45cf34312412d3691a39f003bcd54791ea16542aa3f5a2674d7499c9cc4039550b2cbd32cc3d4c5fe100d65cb05690594b10a0c42dfab63bcca3dac121bb195b

test/functional/rpc_blockchain.py

@@ -549,6 +549,7 @@ def _test_waitforblock(self):
         # The chain has probably already been restored by the time reconsiderblock returns,
         # but poll anyway.
         self.wait_until(lambda: node.waitfornewblock(timeout=100)['hash'] == current_hash)
+        assert_raises_rpc_error(-1, "Negative timeout", node.waitfornewblock, -1)
 
     def _test_waitforblockheight(self):
         self.log.info("Test waitforblockheight")