Fix pylint issues

Author: uvchik

windpowerlib/__init__.py

@@ -2,9 +2,9 @@
 __license__ = "MIT"
 __version__ = "0.2.1dev"
 
-from windpowerlib.wind_turbine import WindTurbine
-from windpowerlib.wind_farm import WindFarm
-from windpowerlib.wind_turbine_cluster import WindTurbineCluster
-from windpowerlib.modelchain import ModelChain
-from windpowerlib.turbine_cluster_modelchain import TurbineClusterModelChain
-from windpowerlib.wind_turbine import get_turbine_types
+from .wind_turbine import WindTurbine
+from .wind_farm import WindFarm
+from .wind_turbine_cluster import WindTurbineCluster
+from .modelchain import ModelChain
+from .turbine_cluster_modelchain import TurbineClusterModelChain
+from .wind_turbine import get_turbine_types

windpowerlib/power_curves.py

@@ -159,7 +159,7 @@ def smooth_power_curve(power_curve_wind_speeds, power_curve_values,
         # Get standard deviation for Gauss function
         standard_deviation = (
             (power_curve_wind_speed * normalized_standard_deviation + 0.6)
-            if standard_deviation_method is "Staffell_Pfenninger"
+            if standard_deviation_method == "Staffell_Pfenninger"
             else power_curve_wind_speed * normalized_standard_deviation
         )
         # Get the smoothed value of the power output

windpowerlib/wind_farm.py

@@ -9,7 +9,6 @@
 from windpowerlib import tools, power_curves, WindTurbine
 import numpy as np
 import pandas as pd
-import logging
 import warnings