Improve two error messages.

diff --git a/include/deal.II/lac/affine_constraints.h b/include/deal.II/lac/affine_constraints.h
index c46dda29b7d52b428c21fa75afe9c7db776fc378..e683d2d8c4ecdec06e0fa5f046d4b86ad9bdd6c8 100644 (file)
--- a/include/deal.II/lac/affine_constraints.h
+++ b/include/deal.II/lac/affine_constraints.h
@@ -1879,13 +1879,25 @@ public:
    *
    * @ingroup Exceptions
    */
-  DeclException0(ExcMatrixIsClosed);
+  DeclExceptionMsg(
+    ExcMatrixIsClosed,
+    "You are attempting an operation on an AffineConstraints object "
+    "that requires the object to be 'closed', i.e., for which you "
+    "needed to call the close() member function. But the object "
+    "is not currently closed, and so the operation can not be "
+    "performed.");
   /**
    * Exception
    *
    * @ingroup Exceptions
    */
-  DeclException0(ExcMatrixNotClosed);
+  DeclExceptionMsg(
+    ExcMatrixNotClosed,
+    "You are attempting an operation on an AffineConstraints object "
+    "that requires the object to not be 'closed', i.e., for which you "
+    "must not already have called the close() member function. But the "
+    "object is already closed, and so the operation can not be "
+    "performed.");
   /**
    * Exception
    *