Merge branch 'py3_compatibility' into '1.5.x'

beat/backend/python/algorithm.py

beat/backend/python/baseformat.py

beat/backend/python/data.py

beat/backend/python/database.py

beat/backend/python/dataformat.py

beat/backend/python/executor.py

beat/backend/python/hash.py

beat/backend/python/helpers.py

beat/backend/python/library.py

beat/backend/python/message_handler.py

beat/backend/python/scripts/databases_provider.py

beat/backend/python/scripts/execute.py

beat/backend/python/test/test_databases_index.py

beat/backend/python/test/test_databases_provider.py

beat/backend/python/test/test_dbexecutor.py

beat/backend/python/test/test_executor.py

beat/backend/python/test/test_format_simple.py

beat/backend/python/test/test_hash.py

beat/backend/python/test/test_message_handler.py