Revert "Capture ctrl-c in presubmit multiprocessing pool"

This reverts commit 873c28d1.

Reason for revert: Broken on Windows (crbug.com/762389)

Original change's description:
> Capture ctrl-c in presubmit multiprocessing pool
> 
> Presubmit spins up lots of multiprocessing processes to run
> each individual test. If you cancel your presubmit run with
> <ctrl>+c, that signal gets passed through to each of those,
> which then raises its own KeyboardInterrupt, and prints its
> own stacktrace.
> 
> This change has each member of the multiprocessing pool instead
> exit gracefully (albeit with an error code) so that only the
> parent process prints its stacktrace.
> 
> R=​michaelpg@chromium.org
> 
> Bug: 635196
> Change-Id: If9081910a359889a43bc1b72c91a859ebe37a1d6
> Reviewed-on: https://chromium-review.googlesource.com/651764
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> Commit-Queue: Aaron Gable <agable@chromium.org>

TBR=iannucci@chromium.org,agable@chromium.org,michaelpg@chromium.org

Change-Id: Ib8e5b2f59b0060dfbfbeba348e211db292318b3b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 635196
Reviewed-on: https://chromium-review.googlesource.com/653434Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>

presubmit_support.py

@@ -30,7 +30,6 @@ import os  # Somewhat exposed through the API.
 import pickle  # Exposed through the API.
 import random
 import re  # Exposed through the API.
-import signal
 import sys  # Parts exposed through API.
 import tempfile  # Exposed through the API.
 import time
@@ -436,19 +435,11 @@ class InputApi(object):
 
     self.cpu_count = multiprocessing.cpu_count()
 
-    # We initialize here because in RunTests, the current working directory has
+    # this is done here because in RunTests, the current working directory has
     # changed, which causes Pool() to explode fantastically when run on windows
     # (because it tries to load the __main__ module, which imports lots of
     # things relative to the current working directory).
-    # We capture ctrl-c in the initializer to prevent massive console spew when
-    # cancelling all of the processes with ctrl-c.
-    def _capture_interrupt():
-      CTRL_C = signal.SIGINT
-      if sys.platform == 'win32':
-        CTRL_C = signal.CTRL_C_EVENT
-      signal.signal(CTRL_C, lambda x, y: sys.exit(1))
-    self._run_tests_pool = multiprocessing.Pool(
-        self.cpu_count, _capture_interrupt)
+    self._run_tests_pool = multiprocessing.Pool(self.cpu_count)
 
     # The local path of the currently-being-processed presubmit script.
     self._current_presubmit_path = os.path.dirname(presubmit_path)

tests/presubmit_unittest.py

@@ -165,8 +165,8 @@ class PresubmitUnittest(PresubmitTestsBase):
       'git_footers', 'glob', 'inspect', 'json', 'load_files', 'logging',
       'marshal', 'normpath', 'optparse', 'os', 'owners', 'owners_finder',
       'pickle', 'presubmit_canned_checks', 'random', 're', 'rietveld', 'scm',
-      'signal', 'subprocess', 'sys', 'tempfile', 'time', 'traceback', 'types',
-      'unittest', 'urllib2', 'warn', 'multiprocessing', 'DoGetTryMasters',
+      'subprocess', 'sys', 'tempfile', 'time', 'traceback', 'types', 'unittest',
+      'urllib2', 'warn', 'multiprocessing', 'DoGetTryMasters',
       'GetTryMastersExecuter', 'itertools', 'urlparse', 'gerrit_util',
       'GerritAccessor',
     ]