Better error message from deployment failure

This commit modifies `deploy_tester_contract()` so it raises
an exception with a message with failed `require()`s.

Before this commit, `deploy_tester_contract()` did not raise an
exception when the deployment failed for a `require()` condition.

This solves raiden-network#1329.

raiden_contracts/tests/fixtures/base/web3_fixtures.py

@@ -4,7 +4,7 @@
 import pytest
 from eth_tester import EthereumTester, PyEVMBackend
 from web3 import Web3
-from web3.contract import ContractFunction
+from web3.contract import ContractConstructor, ContractFunction
 from web3.providers.eth_tester import EthereumTesterProvider
 
 from raiden_contracts.tests.utils.constants import (
@@ -77,12 +77,22 @@ def auto_revert_chain(web3: Web3) -> Generator:
 def _call_and_transact(
     contract_function: ContractFunction, transaction_params: Optional[Dict] = None
 ) -> str:
-    """ Executes contract_function.{call, transaction}(transaction_params) and returns txhash """
-    # First 'call' might raise an exception
+    """ Executes contract_function.{call, transact}(transaction_params) and returns txhash """
+    # First 'call' might raise an exception, containing an error message from require().
     contract_function.call(transaction_params)
     return contract_function.transact(transaction_params)
 
 
+def _estimate_gas_and_transact_constructor(
+    contract_constructor: ContractConstructor, transaction_params: Optional[Dict] = None
+) -> str:
+    """ Execute contract_constructor.{estimateGas, transact}(transaction_params); return txhash """
+    # First 'estimate_gas' might raise an exception, containing an error message from require().
+    contract_constructor.estimateGas(transaction_params)
+    return contract_constructor.transact(transaction_params)
+
+
 @pytest.fixture(scope="session", autouse=True)
 def call_and_transact() -> None:
     ContractFunction.call_and_transact = _call_and_transact
+    ContractConstructor.call_and_transact = _estimate_gas_and_transact_constructor

raiden_contracts/tests/fixtures/contracts.py

@@ -38,8 +38,7 @@ def fn(
         web3: Web3, deployer_address: HexAddress, abi: List, bytecode: str, **kwargs: Dict
     ) -> str:
         contract = web3.eth.contract(abi=abi, bytecode=bytecode)
-        # Failure does not fire an exception.  Check the receipt for status.
-        return contract.constructor(**kwargs).transact({"from": deployer_address})
+        return contract.constructor(**kwargs).call_and_transact({"from": deployer_address})
 
     return fn