Successful tests should not raise exceptions

dune/solvers/test/multigridtest.cc

@@ -187,8 +187,7 @@ int main(int argc, char** argv) try
     return passed ? 0 : 1;
 }
 catch (Dune::Exception e) {
-
     std::cout << e << std::endl;
-
+    return 1;
 }