ext: Remove dead code from handlers.py

This has been tested with vulture:
https://pypi.org/project/vulture

JIRA: https://gem5.atlassian.net/projects/GEM5/issues/GEM5-533

Change-Id: If878ea1900e2bcd76646b9860f2cc3f808bc5082
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30239
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>

ext/testlib/handlers.py

@@ -44,11 +44,10 @@ import testlib.helper as helper
 import testlib.log as log
 import testlib.result as result
 import testlib.state as state
-import testlib.test_util as test
 import testlib.terminal as terminal
 
 from six.moves import queue as Queue
-from testlib.configuration import config, constants
+from testlib.configuration import constants
 
 
 class _TestStreamManager(object):
@@ -194,8 +193,6 @@ class SummaryHandler(object):
             state.Result.Passed: color.Green,
             state.Result.Skipped: color.Cyan,
     }
-    sep_fmtkey = 'separator'
-    sep_fmtstr = '{%s}' % sep_fmtkey
 
     def __init__(self):
         self.mapping = {
@@ -333,9 +330,6 @@ class TerminalHandler(object):
     def close(self):
         pass
 
-    def set_verbosity(self, verbosity):
-        self.verbosity = verbosity
-
 class MultiprocessingHandlerWrapper(object):
     '''
     A handler class which forwards log records to subhandlers, enabling