Due to some security concerns raised today, all core devs decided to delay the hard fork.
See:
- https://medium.com/chainsecurity/constantinople-enables-new-reentrancy-attack-ace4088297d9
- https://gitter.im/ethereum/AllCoreDevs?at=5c3e0fb51cb70a372ae2c1f7
We delayed the Constantinople VM in this PR: https://github.com/ethereum/trinity/pull/176