e9e939108 [tests] Check connectivity before sending in assumevalid.py (John Newbery)
Pull request description:
assumevalid.py would try to send over a closed P2P connection in a loop,
hitting the following failure many times:
`TestFramework.mininode (ERROR): Cannot send message. No connection to node!`
The test still passed, but this is a lot of noise in the test log.
Just check that the connection is open before trying to send.
Tree-SHA512: 6faf2ce5717de976fed1b5c863bc8d17e785928690f833d5bf175178f95d39f455635a844fe7e0dfdad83ae779dd45bc6e4ed89a9467d8482c5be73b55095c8d
We only want to verify that assumevalid causes block 102 to be accepted
even though it contains an invalid script, so there is no need to send
more blocks.
Dash has only 1/4 of block time compared to Bitcoin, which requires 4 times
the amount of headers so that the assumevalid check in ConnectBlock results
in skipping of script checks.
Using so many headers now causes block time validation to fail (too far in
the future), so we need to adjust mock time as well.
