[3.15] Add "new in 3.15" comments to idlelib (GH-153052) (#153054)

Add "new in 3.15" comments to idlelib (GH-153052)

Lazy keyword added to colorizer and test in PR-GH-142351.
Tested NameError hint expanded in PR-GH-144299.
(cherry picked from commit 0621639)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Author: miss-islington

Lib/idlelib/colorizer.py

@@ -42,7 +42,7 @@ def make_pat():
         ]) +
         r"))"
     )
-    lazy_softkw = (
+    lazy_softkw = (  # lazy new in 3.15 (+ 2 lines below).
         r"^[ \t]*" +  # at beginning of line + possible indentation
         r"(?P<LAZY_SOFTKW>lazy)" +
         r"(?=[ \t]+(?:import|from)\b)"  # followed by 'import' or 'from'

Lib/idlelib/idle_test/test_colorizer.py

@@ -542,7 +542,7 @@ def test_case_soft_keyword(self):
         self._assert_highlighting('case _:', {'KEYWORD': [('1.0', '1.4'),
                                                           ('1.5', '1.6')]})
 
-    def test_lazy_soft_keyword(self):
+    def test_lazy_soft_keyword(self):  # lazy new in 3.15.
         # lazy followed by import
         self._assert_highlighting('lazy import foo',
                                   {'KEYWORD': [('1.0', '1.4'),

Lib/idlelib/idle_test/test_run.py

@@ -44,7 +44,7 @@ def __eq__(self, other):
                                "Or did you forget to import 'abc'?\n"),
             ('int.reel', AttributeError,
                  "type object 'int' has no attribute 'reel'. "
-                 "Did you mean '.real' instead of '.reel'?\n"),
+                 "Did you mean '.real' instead of '.reel'?\n"),  # More in 3.15.
             )
 
     @force_not_colorized