Fix bug in detecting unused-variable when iterating on variable.

doc/whatsnew/fragments/3044.bugfix

@@ -0,0 +1,3 @@
+Fix bug in detecting ``unused-variable`` when iterating on variable.
+
+Closes #3044

pylint/checkers/variables.py

@@ -2388,7 +2388,7 @@ def _check_is_unused(
             self._check_unused_arguments(name, node, stmt, argnames, nonlocal_names)
         else:
             if stmt.parent and isinstance(
-                stmt.parent, (nodes.Assign, nodes.AnnAssign, nodes.Tuple)
+                stmt.parent, (nodes.Assign, nodes.AnnAssign, nodes.Tuple, nodes.For)
             ):
                 if name in nonlocal_names:
                     return

tests/functional/u/unused/unused_variable.py

@@ -186,3 +186,16 @@ def sibling_except_handlers():
         pass
     except ValueError as e:
         print(e)
+
+def func6():
+    a = 1
+
+    def nonlocal_writer():
+        nonlocal a
+
+        for a in range(10):
+            pass
+
+    nonlocal_writer()
+
+    assert a == 9, a