Improve output

python/dune/perftool/pdelab/driver.py

@@ -865,7 +865,7 @@ def exact_solution_from_dirichlet():
             "  if (std::abs(native({})[i]-native({})[i]) > maxerror)".format(v, solution),
             "    maxerror = std::abs(native({})[i]-native({})[i]);".format(v, solution),
             "",
-            "std::cout << maxerror << std::endl;",
+            "std::cout << \"Maxerror: \" << maxerror << std::endl;",
             "",
             "if (maxerror>1e-14)",
             "  throw;"]