message: Change function signature.
  This function does not need to return a remaining balance as the balance
  is unchanged during the operation.
diff: @@ -205,7 +205,7 @@ pub(crate) fn create_unbonding_purse<P: Auction + ?Sized>(
  unbonder_public_key: PublicKey,
  bonding_purse: URef,
  amount: U512,
  -) -> Result<U512> {
  +) -> Result<()> {
  if provider.get_balance(bonding_purse)?.unwrap_or_default() < amount {
  return Err(Error::UnbondTooLarge);
  }
  @@ -225,10 +225,7 @@ pub(crate) fn create_unbonding_purse<P: Auction + ?Sized>(
  .push(new_unbonding_purse);
  set_unbonding_purses(provider, unbonding_purses)?;
  - // Remaining motes in the validator's bid purse
  - let remaining_bond = provider.get_balance(bonding_purse)?.unwrap_or_default();
  -
  - Ok(remaining_bond)
  + Ok(())
  }
  /// Reinvests delegator reward by increasing its stake.
  