The test still pass on my Fedora 29 with:

diff --git a/Lib/idlelib/idle_test/test_squeezer.py b/Lib/idlelib/idle_test/test_squeezer.py
index 71eccd3693..e026567789 100644
--- a/Lib/idlelib/idle_test/test_squeezer.py
+++ b/Lib/idlelib/idle_test/test_squeezer.py
@@ -114,7 +114,7 @@ class SqueezerTest(unittest.TestCase):
         if root is None:
             root = get_test_tk_root(self)
         text_widget = Text(root)
-        text_widget["font"] = ('Courier', 10)
+        text_widget["font"] = ('XXXX', 10)
         text_widget.mark_set("iomark", "1.0")
         return text_widget
 
@@ -300,7 +300,7 @@ class SqueezerTest(unittest.TestCase):
         orig_auto_squeeze_min_lines = squeezer.auto_squeeze_min_lines
 
         # Increase both font size and auto-squeeze-min-lines.
-        text_widget["font"] = ('Courier', 20)
+        text_widget["font"] = ('XXXX', 20)
         new_auto_squeeze_min_lines = orig_auto_squeeze_min_lines + 10
         self.set_idleconf_option_with_cleanup(
             'main', 'PyShell', 'auto-squeeze-min-lines',
@@ -309,7 +309,7 @@ class SqueezerTest(unittest.TestCase):
         Squeezer.reload()
         # The following failed on Gentoo buildbots.  Issue title will be
         # IDLE: Fix squeezer test_reload.
-        #self.assertGreater(squeezer.zero_char_width, orig_zero_char_width)
+        self.assertGreater(squeezer.zero_char_width, orig_zero_char_width)
         self.assertEqual(squeezer.auto_squeeze_min_lines,
                          new_auto_squeeze_min_lines)