signrawtransaction is deprecated and will be fully removed in v0.18. To use signrawtransaction in v0.17, restart bitcoind with -deprecatedrpc=signrawtransaction
Projects should transition to using signrawtransactionwithkey and signrawtransactionwithwallet before upgrading to v0.18.
As per the low-level RPC changes introduced in Bitcoin Core v0.17:
/cc @GeorgeKimionis