Improve the text of an assertion.

diff --git a/include/deal.II/numerics/data_out_dof_data.h b/include/deal.II/numerics/data_out_dof_data.h
index e36f78a2b7065a374f9a781aad5b9df1e8f1f5a3..f9b81f6427fbffc25bf28b4530d96fbc4725246f 100644 (file)
--- a/include/deal.II/numerics/data_out_dof_data.h
+++ b/include/deal.II/numerics/data_out_dof_data.h
@@ -66,7 +66,9 @@ namespace Exceptions
     DeclExceptionMsg(ExcNoTriangulationSelected,
                      "For the operation you are attempting, you first need to "
                      "tell the DataOut or related object which DoFHandler or "
-                     "triangulation you would like to work on.");
+                     "triangulation you would like to work on. This is "
+                     "generally done using the 'attach_dof_handler()' or "
+                     "'attach_triangulation()' member functions.");
 
     /**
      * Exception
@@ -74,7 +76,9 @@ namespace Exceptions
     DeclExceptionMsg(ExcNoDoFHandlerSelected,
                      "For the operation you are attempting, you first need to "
                      "tell the DataOut or related object which DoFHandler "
-                     "you would like to work on.");
+                     "you would like to work on. This is "
+                     "generally done using the 'attach_dof_handler()' "
+                     "member function.");
 
     /**
      * Exception