1 files changed, 13 insertions, 2 deletions

diff --git a/src/mailman/core/runner.py b/src/mailman/core/runner.py
index 757d8837e..9f8094153 100644
--- a/src/mailman/core/runner.py
+++ b/src/mailman/core/runner.py
@@ -31,7 +31,8 @@ from mailman.core.logging import reopen
 from mailman.core.switchboard import Switchboard
 from mailman.interfaces.languages import ILanguageManager
 from mailman.interfaces.listmanager import IListManager
-from mailman.interfaces.runner import IRunner, RunnerCrashEvent
+from mailman.interfaces.runner import (
+    IRunner, RunnerCrashEvent, RunnerInterrupt)
 from mailman.utilities.string import expand
 from public import public
 from zope.component import getUtility
@@ -98,6 +99,16 @@ class Runner:
         elif signum == signal.SIGHUP:
             reopen()
             rlog.info('%s runner caught SIGHUP.  Reopening logs.', self.name)
+        # As of Python 3.5, PEP 475 gets in our way.  Runners with long
+        # time.sleep()'s in their _snooze() method (e.g. the retry runner) will
+        # have their system call implemented time.sleep() automatically retried
+        # at the C layer.  The only reliable way to prevent this is to raise an
+        # exception in the signal handler.  The standard run() method
+        # automatically suppresses this exception, meaning, it's caught and
+        # ignored, but effectively breaks the run() loop, which is just what we
+        # want.  Runners which implement their own run() method must be
+        # prepared to catch RunnerInterrupts, usually also ignoring them.
+        raise RunnerInterrupt
 
     def set_signals(self):
         """See `IRunner`."""
@@ -113,7 +124,7 @@ class Runner:
     def run(self):
         """See `IRunner`."""
         # Start the main loop for this runner.
-        with suppress(KeyboardInterrupt):
+        with suppress(KeyboardInterrupt, RunnerInterrupt):
             while True:
                 # Once through the loop that processes all the files in the
                 # queue directory.