Merge https://github.com/freqtrade/freqtrade into personal-branch

freqtrade/strategy/hyper.py

@@ -381,7 +381,8 @@ class HyperStrategyMixin(object):
         if filename.is_file():
             logger.info(f"Loading parameters from file {filename}")
             try:
-                params = json_load(filename.open('r'))
+                with filename.open('r') as f:
+                    params = json_load(f)
                 if params.get('strategy_name') != self.__class__.__name__:
                     raise OperationalException('Invalid parameter file provided.')
                 return params

freqtrade/strategy/interface.py

@@ -65,9 +65,9 @@ class IStrategy(ABC, HyperStrategyMixin):
     _populate_fun_len: int = 0
     _buy_fun_len: int = 0
     _sell_fun_len: int = 0
-    _ft_params_from_file: Dict = {}
+    _ft_params_from_file: Dict
     # associated minimal roi
-    minimal_roi: Dict
+    minimal_roi: Dict = {}
 
     # associated stoploss
     stoploss: float