presubmit_support: Use six instead of future.utils for raise_from.

This fixes CL:2880843 to use a module already present in vpython.

Bug: 1206782
Change-Id: If4158a62011e043e89f40f368c9c644434df6614
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2901758
Commit-Queue: Allen Webb <allenwebb@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>

presubmit_support.py

@@ -29,6 +29,7 @@ import os  # Somewhat exposed through the API.
 import random
 import re  # Exposed through the API.
 import signal
+import six
 import sys  # Parts exposed through API.
 import tempfile  # Exposed through the API.
 import threading
@@ -1659,20 +1660,16 @@ class PresubmitExecuter(object):
     try:
       result = eval(function_name + '(*__args)', context)
       self._check_result_type(result)
-    except Exception as e:
+    except Exception:
       if sink:
         elapsed_time = time_time() - start_time
         sink.report(function_name, rdb_wrapper.STATUS_FAIL, elapsed_time)
-      # TODO(crbug.com/953884): replace raise_from with native py3:
+      # TODO(crbug.com/953884): replace reraise with native py3:
       #   raise .. from e
-      try:
+      e_type, e_value, e_tb = sys.exc_info()
-        from future.utils import raise_from
+      six.reraise(e_type, 'Evaluation of %s failed: %s' % (function_name,
-        raise_from(type(e)('Evaluation of %s failed: %s' % (function_name, e)),
+                                                           e_value),
-                   e)
+                  e_tb)
-      except ImportError:
-        if self.verbose:
-          traceback.print_exc()
-        raise type(e)('Evaluation of %s failed: %s' % (function_name, e))
 
     if sink:
       elapsed_time = time_time() - start_time