[Autotest][PY3] Migrating client/cros (kernel_trace -> rtc)

Migrating client/cros from kernel_trace.py -> rtc.py to python3.

BUG=chromium:990593
TEST= py_compile in py2 and py3. CQ. dummy_Pass. policy_ and network_
test

Change-Id: I8cd48c1ab6d0d71f6fcf2573fda6a5badda957b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2488642
Reviewed-by: Seewai Fu <seewaifu@google.com>
Reviewed-by: Greg Edelston <gredelston@google.com>
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
Tested-by: Derek Beckett <dbeckett@chromium.org>
diff --git a/client/cros/p2p_utils.py b/client/cros/p2p_utils.py
index 0a751b1..dee00c9 100644
--- a/client/cros/p2p_utils.py
+++ b/client/cros/p2p_utils.py
@@ -1,3 +1,4 @@
+# Lint as: python2, python3
 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
@@ -31,8 +32,8 @@
             shutil.rmtree(backup_path)
         if os.path.exists(P2P_SHARE_PATH):
             os.rename(P2P_SHARE_PATH, backup_path)
-    except OSError, e:
-        raise error.TestError("Error on P2P files backup: %s" % (e.message))
+    except OSError as e:
+        raise error.TestError("Error on P2P files backup: %s" % (str(e)))
 
 
 def p2p_restore_files(backup_path=P2P_SHARE_BACKUP_PATH):