gh-154395: Skip test_environment_is_not_modified without rl_change_environment (GH-154396)

readline sets LINES and COLUMNS if rl_change_environment is not
available, which is the case with readline older than 6.3.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: serhiy-storchaka

Lib/test/test_readline.py

@@ -5,6 +5,7 @@
 import locale
 import os
 import sys
+import sysconfig
 import tempfile
 import textwrap
 import threading
@@ -413,6 +414,8 @@ def test_write_read_limited_history(self):
         # So, we've only tested that the read did not fail.
         # See TestHistoryManipulation for the full test.
 
+    @unittest.skipUnless(sysconfig.get_config_var("HAVE_RL_CHANGE_ENVIRONMENT"),
+                         "readline can modify the environment")
     def test_environment_is_not_modified(self):
         # os.environ contains environment at the time "os" module was loaded, so
         # before the "readline" module is loaded.