beginnings of using ErrCtx

src/unix2db/main.zig

@@ -73,12 +73,16 @@ fn execute(
     defer groupFile.close();
 
     var err_ctx = ErrCtx{};
-
     var users = try User.fromReader(
         allocator,
-        err_ctx.writer(),
+        &err_ctx,
         passwdFile.reader(),
     );
+    errdefer {
+        var it = err_ctx.iterator();
+        while (it.next()) |err|
+            std.debug.print("ERROR: {s}\n", .{err});
+    }
     defer for (users) |*user| user.deinit(allocator);
     defer allocator.free(users);