Fix bug in TraceInfo._log_error() where the real exception obj was hi…

…ding behind 'ExceptionWithTraceback' (#7930)

* Fix bug in TraceInfo._log_error() where the real exception obj was hiding behind 'ExceptionWithTraceback'

* Commit 629bc63 introduced a bug in test_execute_jail_failure.
This reverts the bug in the test, now that the real bug is fixed in the TraceInfo._log_error() method

celery/app/trace.py

@@ -10,7 +10,7 @@
 from collections import namedtuple
 from warnings import warn
 
-from billiard.einfo import ExceptionInfo
+from billiard.einfo import ExceptionInfo, ExceptionWithTraceback
 from kombu.exceptions import EncodeError
 from kombu.serialization import loads as loads_message
 from kombu.serialization import prepare_accept_content
@@ -238,6 +238,8 @@ def handle_failure(self, task, req, store_errors=True, call_errbacks=True):
 
     def _log_error(self, task, req, einfo):
         eobj = einfo.exception = get_pickled_exception(einfo.exception)
+        if isinstance(eobj, ExceptionWithTraceback):
+            eobj = einfo.exception = eobj.exc
         exception, traceback, exc_info, sargs, skwargs = (
             safe_repr(eobj),
             safe_str(einfo.traceback),

t/unit/worker/test_request.py

@@ -155,7 +155,7 @@ def test_execute_jail_failure(self):
             self.app, uuid(), self.mytask_raising.name, {}, [4], {},
         )
         assert isinstance(ret, ExceptionInfo)
-        assert ret.exception.exc.args == (4,)
+        assert ret.exception.args == (4,)
 
     def test_execute_task_ignore_result(self):
         @self.app.task(shared=False, ignore_result=True)