Minor change add missing single quotation mark

Author: birgits

tests/test_wind_turbine.py

@@ -75,6 +75,6 @@ def test_wrongly_defined_to_group_method(self):
            'path': self.source}
         e_t_1 = WindTurbine(**example_turbine)
         with pytest.raises(ValueError,
-                           match="The 'number' and the 'total_capacity"
-                                 " parameter are mutually exclusive."):
+                           match="The 'number' and the 'total_capacity' "
+                                 "parameter are mutually exclusive."):
             e_t_1.to_group(5, 3000)

windpowerlib/wind_turbine.py

@@ -250,7 +250,7 @@ def to_group(self, number_turbines=None, total_capacity=None):
         """
 
         if number_turbines is not None and total_capacity is not None:
-            raise ValueError("The 'number' and the 'total_capacity parameter "
+            raise ValueError("The 'number' and the 'total_capacity' parameter "
                              "are mutually exclusive. Use just one of them.")
         elif total_capacity is not None:
             number_turbines = total_capacity / self.nominal_power