For example, previously an eth_call may have returned this:
{'id': 2, 'jsonrpc': '2.0', 'result': '0x'}
And now under 1.9.15, it will return this:
{'error': {'code': -32000,
'message': 'insufficient funds for gas * price + value'},
'id': 2,
'jsonrpc': '2.0'}
Another example is for reverts, previous results would be encoded with an error hex like this:
{'id': 1337,
'jsonrpc': '2.0',
'result': '0x08c379a00000...}
In 1.9.15, this now has a revert reason:
{'error': {'code': 3,
'data': '0x08c379a...',
'message': 'execution reverted: HAS_NEVER_OWNED_KEY'},
'id': 1337,
'jsonrpc': '2.0'}