running regtest network, bitcoin.conf incorrectly configured?
just do this... 

To use bitcoind and bitcoin-cli, you will need to add a RPC password to your bitcoin.conf file. Both programs will read from the same file if both run on the same system as the same user, so any long random password will work:

  rpcpassword=change_this_to_a_long_random_password


in the future I'll be sure to RTFM