fix strings to new convention

Author: gboehl

econpizza/solvers/steady_state.py

@@ -162,8 +162,7 @@ def solve_stst(self, tol=1e-8, maxit=15, tol_backwards=None, maxit_backwards=200
     if mess:
         not_var_nor_par = list(
             set(self['steady_state']['fixed_values']) - set(evars) - set(par_names))
-        mess += f"Fixed value(s) ``{'``, ``'.join(not_var_nor_par)
-                                    }`` " + f"not declared. " if not_var_nor_par else ''
+        mess += f"Fixed value(s) ``{'``, ``'.join(not_var_nor_par)}`` not declared. " if not_var_nor_par else ''
 
     if err > tol or not res['success']:
         if not res["success"] or raise_errors: