Unify `ValidationError`

[pipermerriam]

What is wrong?

https://github.com/ethereum/py-evm/pull/1089/files#r206404376

As noted in this comment, there is a valid concern that our duplicate ValidationError exceptions could easily be mixed up, causing us to not be catching the exception we think we are catching.

How can it be fixed

Once ethereum/eth-utils#114 has been done, modify the codebase to use that exception class for all ValidationError exceptions.

[carver]

It could potentially go in eth_utils.exceptions.ValidationError.

[pipermerriam]

ethereum/eth-utils#114

[glaksmono]

Would like to take on this once ethereum/eth-utils#114 is done. Seems like there is already a PR on the issue @pipermerriam @carver

[pipermerriam]

@glaksmono just released and published eth-utils==1.1.1 which contains the new ValidationError. Go for it 👍