Fix typo

Author: brownbaerchen

pySDC/helpers/spectral_helper.py

@@ -595,7 +595,7 @@ def get_Neumann_BC_row(self, x):
         elif x == 1:
             return nn
         else:
-            raise NotImplementedError(f'Don\'t know how to generate Dirichlet BC\'s at {x=}!')
+            raise NotImplementedError(f'Don\'t know how to generate Neumann BC\'s at {x=}!')
 
     def get_Dirichlet_recombination_matrix(self):
         '''