eth-tester-error-01.txt

    @pytest.fixture
    def base_tester():
>       return EthereumTester(PyEVMBackend())

tests/conftest.py:246: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
venv/lib/python3.6/site-packages/eth_tester/backends/pyevm/main.py:262: in __init__
    self.reset_to_genesis()
venv/lib/python3.6/site-packages/eth_tester/backends/pyevm/main.py:293: in reset_to_genesis
    self.account_keys, self.chain = setup_tester_chain()
venv/lib/python3.6/site-packages/eth_tester/backends/pyevm/main.py:144: in setup_tester_chain
    chain = MainnetTesterChain.from_genesis(db, genesis_params, genesis_state)
venv/lib/python3.6/site-packages/evm/chains/base.py:324: in from_genesis
    account_db.persist()
venv/lib/python3.6/site-packages/evm/db/account.py:399: in persist
    self._batchtrie.commit(apply_deletes=False)
venv/lib/python3.6/site-packages/evm/db/batch.py:45: in commit
    self.diff().apply_to(self.wrapped_db, apply_deletes)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <evm.db.diff.DBDiff object at 0x10a20ccf8>, db = <evm.db.chain.ChainDB object at 0x10a29b860>, apply_deletes = False

    def apply_to(self, db: MutableMapping, apply_deletes: bool = True) -> None:
        """
            Apply the changes in this diff to the given database.
            You may choose to opt out of deleting any underlying keys.
    
            :param apply_deletes: whether the pending deletes should be
                applied to the database
            """
        for key, value in self._changes.items():
            if value is DELETED:
                if apply_deletes:
                    try:
                        del db[key]
                    except KeyError:
                        pass
                else:
                    pass
            else:
>               db[key] = value
E               TypeError: 'ChainDB' object does not support item assignment