Undefined names in __all__

[cclauss]

flake8 testing of https://github.com/qunarcorp/open_dnsdb on Python 3.7.1

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./dnsdb_common/library/utils.py:23:1: F822 undefined name 'is_subnet_public' in __all__
__all__ = (
^
./dnsdb_common/library/utils.py:23:1: F822 undefined name 'load_config_option' in __all__
__all__ = (
^
./dnsdb_common/library/utils.py:23:1: F822 undefined name 'is_valid_ip_bysocketis_string' in __all__
__all__ = (
^
3     F822 undefined name 'is_subnet_public' in __all__
3

E901,E999,F821,F822,F823 are the "showstopper" flake8 issues that can halt the runtime with a SyntaxError, NameError, etc. These 5 are different from most other flake8 issues which are merely "style violations" -- useful for readability but they do not effect runtime safety.

• F821: undefined name name
• F822: undefined name name in __all__
• F823: local variable name referenced before assignment
• E901: SyntaxError or IndentationError
• E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree

[LostSymbol]

Fixed that. Thank you very much!