[Perf] Update references to telemetry.core.discover

tools/perf/profile_creators/profile_generator.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Handles generating profiles and transferring them to/from mobile devices."""
 
 import logging
 import optparse
 import os
 import shutil
 import stat
 import sys
 import tempfile
 
 from profile_creators import profile_extender
-from telemetry.core import discover
 from telemetry.core import util
 from telemetry.internal import story_runner
 from telemetry.internal.browser import browser_finder
 from telemetry.internal.browser import browser_options
 from telemetry.internal.util import binary_manager
 
+from py_utils import discover
 
 def _DiscoverProfileExtenderClasses():
   profile_extenders_dir = (
       os.path.abspath(
           os.path.join(
               util.GetBaseDir(), '..', 'perf',
               'profile_creators')))
   base_dir = os.path.abspath(os.path.join(profile_extenders_dir, '..'))
 
   profile_extenders_unfiltered = discover.DiscoverClasses(
@@ skipping 174 matching lines @@
   ProcessCommandLineArgs(parser, options)
 
   # Generate profile.
   profile_extenders = _DiscoverProfileExtenderClasses()
   profile_extender_class = profile_extenders[options.profile_type_to_generate]
 
   generator = ProfileGenerator(profile_extender_class,
                                options.profile_type_to_generate)
   generator.Create(options, options.output_dir)
   return 0