message: Wait for 3 seconds after invalidateblock() before checking for assertions
  Add 3 sec waitFor() after invalidateblock(), this is mainly done to avoid Travis
  failures. We are going to probably remove it once we move to gitlab.com
diff: @@ -7,7 +7,7 @@ This test checks activation of OP_CHECKDATASIG
  """
  import test_framework.loginit
  from test_framework.test_framework import ComparisonTestFramework
  -from test_framework.util import satoshi_round, assert_equal, assert_raises_rpc_error, start_node
  +from test_framework.util import waitFor, satoshi_round, assert_equal, assert_raises_rpc_error, start_node
  from test_framework.comptool import TestManager, TestInstance, RejectResult
  from test_framework.blocktools import *
  from test_framework.script import *
  @@ -178,10 +178,10 @@ class CheckDataSigActivationTest(ComparisonTestFramework):
  assert(tx0id not in set(node.getrawmempool()))
  node.invalidateblock(format(nov152018forkblock.sha256, 'x'))
  - assert(tx0id in set(node.getrawmempool()))
  + waitFor(3, lambda: tx0id in set(node.getrawmempool()), "Transaction shoud be included in the mempool")
  node.invalidateblock(format(fork_block.sha256, 'x'))
  - assert(tx0id not in set(node.getrawmempool()))
  + waitFor(3, lambda: tx0id not in set(node.getrawmempool()), "Transaction should not be included in the memopool")
  if __name__ == '__main__':
  