📝 Add a change note for PR #3598

Author: webknjaz

docs/changelog/3598.bugfix.rst

@@ -0,0 +1,6 @@
+The :func:`tox_extend_envs() hook <tox.plugin.spec.tox_extend_envs>`
+recently added in :pull:`3591` turned out to not work well with
+``tox run``. It was fixed internally, not to exhaust the underlying
+iterator on the first use.
+
+-- by :user:`webknjaz`