[autotest] Make cros/faft/rpc_functions.py Python 3-compatible syntactically

BUG=chromium:990593
TEST=python3 -m py_compile .../rpc_functions.py

Change-Id: I41b7abe551454c57a1f9fd977980ea1c9a88ad9f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2444889
Reviewed-by: Derek Beckett <dbeckett@chromium.org>
Commit-Queue: Gregory Nisbet <gregorynisbet@google.com>
Tested-by: Gregory Nisbet <gregorynisbet@google.com>
diff --git a/client/cros/faft/rpc_functions.py b/client/cros/faft/rpc_functions.py
index 4957c0d..0515c14 100644
--- a/client/cros/faft/rpc_functions.py
+++ b/client/cros/faft/rpc_functions.py
@@ -7,11 +7,15 @@
 
 @note: When adding categories, please also update server/cros/faft/rpc_proxy.pyi
 """
+
+from __future__ import print_function
+
 import binascii
 import httplib
 import logging
 import os
 import signal
+import six
 import sys
 import tempfile
 import traceback
@@ -139,7 +143,7 @@
                             traceback.format_exception_only(exc_class, exc))
                     exc = xmlrpclib.Fault(
                             fault_code, '%s. %s' % (message, exc_str.rstrip()))
-                raise exc, None, tb
+                six.reraise(exc, None, tb)
             finally:
                 del exc_info
                 del tb