React to pandas FutureWarning

FutureWarning: Sorting because non-concatenation axis is not aligned. A
future version
of pandas will change to not sort by default.

To accept the future behavior, pass 'sort=False'.

To retain the current behavior and silence the warning, pass
'sort=True'.

Author: SabineHaas

windpowerlib/wind_farm.py

@@ -261,7 +261,7 @@ def assign_power_curve(self, wake_losses_model='power_efficiency_curve',
                 if power_curve.iloc[0]['wind_speed'] != 0.0:
                     power_curve = pd.concat(
                         [power_curve, pd.DataFrame(data={
-                            'power': [0.0], 'wind_speed': [0.0]})])
+                            'power': [0.0], 'wind_speed': [0.0]})], sort=True)
                 if power_curve.iloc[-1]['power'] != 0.0:
                     power_curve = pd.concat(
                         [power_curve, pd.DataFrame(data={