Style guide fix for W503 W504

CONTRIBUTING.md

@@ -148,6 +148,34 @@ Thus we setup the following rules:
 
 ### Coding Style
 
+#### General Style
+
+In this section we are going to see style rules that should be followed across all languages.
+
+**Line breaks after operators**
+
+For long expressions where we break the expression at the operators the line break should come **after** the operator and not before.
+
+The following should be avoided:
+
+```python
+        participant1_amount = (
+            participant1_state.deposit
+            + participant2_state.transferred_amount
+            - participant1_state.transferred_amount
+        );
+```
+
+instead it should be:
+
+```python
+        participant1_amount = (
+            participant1_state.deposit +
+            participant2_state.transferred_amount -
+            participant1_state.transferred_amount
+        );
+```
+
 #### Python
 
 Raiden is written in Python and we follow the official Python style guide

raiden/network/blockchain_service.py

@@ -63,7 +63,7 @@ def is_synced(self) -> bool:
 
         return True
 
-    def estimate_blocktime(self, oldest: int=256) -> float:
+    def estimate_blocktime(self, oldest: int = 256) -> float:
         """Calculate a blocktime estimate based on some past blocks.
         Args:
             oldest: delta in block numbers to go back.

setup.cfg

@@ -1,10 +1,10 @@
 [flake8]
-ignore = E731, E402
+ignore = E731, E402, W504
 max-line-length = 99
 exclude = raiden/ui/web/node_modules/
 
 [pep8]
-ignore = E731, E402
+ignore = E731, E402, W504
 max-line-length = 99
 
 [coverage:run]