exceptions instead of errors for worker

examples/pipeline/in_to_out_python/in_to_out.py

examples/worker/getnext_broker_python/getnext.py

tests/automatic/bug_fixes/worker_python_memleak/memleak.py

.../full_chain/simple_chain_usermeta_python/get_user_meta.py

tests/automatic/worker/worker_api_python/worker_api.py

worker/api/cpp/unittests/test_server_broker.cpp

worker/api/python/asapo_worker.pxd

worker/api/python/asapo_worker.pyx.in