Fix UnicodeDecodeError when failing jobs

Worker handle_exception and move_to_failed_queue couldn't handle a situation where the exception raised had non-ascii characters. This caused a UnicodeDecodeError when trying to format the exception strings.

If on Python 2, ensure strings get decoded before building the exception string.

Closes #482

rq/worker.py

@@ -742,8 +742,9 @@ class Worker(object):
 
     def handle_exception(self, job, *exc_info):
         """Walks the exception handler stack to delegate exception handling."""
-        exc_string = ''.join(traceback.format_exception_only(*exc_info[:2]) +
-                             traceback.format_exception(*exc_info))
+        exc_string = self._get_safe_exception_string(
+            traceback.format_exception_only(*exc_info[:2]) + traceback.format_exception(*exc_info)
+        )
         self.log.error(exc_string, exc_info=True, extra={
             'func': job.func_name,
             'arguments': job.args,
@@ -765,10 +766,16 @@ class Worker(object):
 
     def move_to_failed_queue(self, job, *exc_info):
         """Default exception handler: move the job to the failed queue."""
-        exc_string = ''.join(traceback.format_exception(*exc_info))
+        exc_string = self._get_safe_exception_string(traceback.format_exception(*exc_info))
         self.log.warning('Moving job to {0!r} queue'.format(self.failed_queue.name))
         self.failed_queue.quarantine(job, exc_info=exc_string)
 
+    def _get_safe_exception_string(self, exc_strings):
+        """Ensure list of exception strings is decoded on Python 2 and joined as one string safely."""
+        if sys.version_info[0] < 3:
+            exc_strings = [exc.decode("utf-8") for exc in exc_strings]
+        return ''.join(exc_strings)
+
     def push_exc_handler(self, handler_func):
         """Pushes an exception handler onto the exc handler stack."""
         self._exc_handlers.append(handler_func)

tests/test_worker.py

@@ -15,6 +15,7 @@ import sys
 import pytest
 
 import mock
+from mock import Mock
 
 from tests import RQTestCase, slow
 from tests.fixtures import (create_file, create_file_after_timeout,
@@ -894,3 +895,24 @@ class HerokuWorkerShutdownTestCase(TimeoutTestCase, RQTestCase):
 
         w._horse_pid = 19999
         w.handle_warm_shutdown_request()
+
+
+class TestExceptionHandlerMessageEncoding(RQTestCase):
+    def test_handle_exception_handles_non_ascii_in_exception_message(self):
+        """Test that handle_exception doesn't crash on non-ascii in exception message."""
+        self.worker.handle_exception(Mock(), *self.exc_info)
+
+    def test_move_to_failed_queue_handles_non_ascii_in_exception_message(self):
+        """Test that move_to_failed_queue doesn't crash on non-ascii in exception message."""
+        self.worker.move_to_failed_queue(Mock(), *self.exc_info)
+
+    def setUp(self):
+        super(TestExceptionHandlerMessageEncoding, self).setUp()
+        self.worker = Worker("foo")
+        self.worker._exc_handlers = []
+        self.worker.failed_queue = Mock()
+        # Mimic how exception info is actually passed forwards
+        try:
+            raise Exception(u"💪")
+        except:
+            self.exc_info = sys.exc_info()