'Handlers' object not callable while storing artifacts (cancelled workitem)

2018-08-04 18:03:50,342 ERROR:storage(28856): Could not save artifacts to /home/vmbuilder/ci-working-dir/storage/qt/qtwebengine/f82519dbb0b677f8b0e282b35c988495f5ef23b2/LinuxopenSUSE_42_3x86_64LinuxopenSUSE_42_3x86_64GCCqtci-linux-openSUSE-42.3-x86_64-2de967DeveloperBuild_NoPch/ebb11e95f8a20dbd08344af7dc04e9a616b41207/build_1533502946/artifacts.tar.gz: 'Handlers' object is not callable
Traceback (most recent call last):
File "src/storage.py", line 476, in handle_upload_artifact
shutil.copyfileobj(self.rfile, tf)
File "/home/vmbuilder/qt-ci/env/lib/python3.5/shutil.py", line 73, in copyfileobj
buf = fsrc.read(length)
File "/usr/lib/python3.5/socket.py", line 575, in readinto
return self._sock.recv_into(b)
File "/home/vmbuilder/qt-ci/src/application.py", line 258, in flush_logs
sighup_handler(signum, frame)
TypeError: 'Handlers' object is not callable