message: contrib/signet/miner: --grind-cmd is required for calibrate
  Thanks to muxator for spotting.
diff: @@ -605,7 +605,7 @@ def main():
  sp.add_argument("--descriptor", default=None, type=str, help="Descriptor for block reward payment")
  for sp in [solvepsbt, generate, calibrate]:
  - sp.add_argument("--grind-cmd", default=None, type=str, help="Command to grind a block header for proof-of-work")
  + sp.add_argument("--grind-cmd", default=None, type=str, required=(sp==calibrate), help="Command to grind a block header for proof-of-work")
  args = parser.parse_args(sys.argv[1:])
  