Change PVSystem to Array in Array.get_iam() error message

Author: wfvining

pvlib/pvsystem.py

@@ -1363,7 +1363,7 @@ def get_iam(self, aoi, iam_model='physical'):
             return iam.sapm(aoi, self.module_parameters)
         elif model == 'interp':
             raise ValueError(model + ' is not implemented as an IAM model'
-                             'option for PVSystem')
+                             'option for Array')
         else:
             raise ValueError(model + ' is not a valid IAM model')