Add flake8 plugins and implement small improvements

freqtrade/optimize/backtesting.py

@@ -13,7 +13,7 @@ from typing import Any, Dict, List, NamedTuple, Optional
 from pandas import DataFrame
 from tabulate import tabulate
 
-import freqtrade.optimize as optimize
+from freqtrade import optimize
 from freqtrade import DependencyException, constants
 from freqtrade.arguments import Arguments
 from freqtrade.configuration import Configuration

requirements-dev.txt

@@ -2,6 +2,8 @@
 -r requirements.txt
 
 flake8==3.6.0
+flake8-type-annotations==0.1.0
+flake8-tidy-imports==1.1.0
 pytest==4.1.1
 pytest-mock==1.10.0
 pytest-asyncio==0.10.0