Fix driver import

python/dune/perftool/pdelab/driver/__init__.py

@@ -1419,6 +1419,7 @@ def solve_instationary():
 
     print_residual()
     print_matrix()
+    from dune.perftool.pdelab.driver.error import compare_dofs, compare_L2_squared
     if get_option("exact_solution_expression"):
         if get_option("compare_dofs"):
             compare_dofs()