TypeError: Derived contract must override function "_beforeTokenTransfer"

[abcoathup]

Hi @ebz,

Welcome to the community

Which version of OpenZeppelin Contracts are you using?
I assume you are using a pre-release version of OpenZeppelin Contracts 3.0 but am not sure where you are getting ERC20Mintable from.

Where is ERC20Mintable.sol in OpenZeppelin Contracts 3.0?

The master branch of the repo currently contains the work for the upcoming 3.0 release. For this release, we are removing the current role contracts, which includes MinterRole. Since we are removing this role, we are also removing the ERC20Mintable contract which used it. There will be an alternative to ERC20Mintable and roles in 3.0, but we haven’t built it yet. In the meantime, please continue using ERC20Mintable from the 2.5 release of Contracts, which can be found in the repository in the …

The issue that you are having is due to overriding when using multiple inheritance.
I will need to create an example of how to do this.