fix false warning by flake8 3.6.0

wwwjfy · wwwjfy · commit c645f64211d5 · 2018-10-25T01:02:27.000+08:00
pycodestyle which is contained in flake8 3.6.0 has an issue with syntax `await (await async_func())`. The issue was filed as PyCQA/pycodestyle#811
diff --git a/tox.ini b/tox.ini
@@ -9,7 +9,7 @@ python =
 
 [testenv:flake8]
 basepython=python
-deps=flake8
+deps=flake8==3.5.0
 commands=flake8 gino
 
 [testenv]
