Update src/scifem/solvers.py

Co-authored-by: Jørgen Schartum Dokken <dokken92@gmail.com>

Author: finsberg

src/scifem/solvers.py

@@ -204,7 +204,7 @@ def solve(self, atol=1e-6, rtol=1e-8, beta=1.0) -> int:
                 self._post_solve_callback(self)
 
             # Compute norm of update
-            residual = self.dx.norm(0)
+            residual = self.dx.norm(PETSc.NormType.NORM_2)
             if i == 1:
                 self.residual_0 = residual
             relative_residual = residual / max(self.residual_0, atol)