ImportError: cannot import name 'BASE_DIR'但是不影响运行，这是什么原因？

Question

debug结果如下：

Connected to pydev debugger (build 191.6183.50)

Traceback (most recent call last):

  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1741, in <module>

    main()

  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1735, in main

    globals = debugger.run(setup['file'], None, None, is_module)

  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\pydevd.py", line 1135, in run

    pydev_imports.execfile(file, globals, locals)  # execute the script

  File "D:\Program Files\Pycharm\PyCharm 2019.1\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile

    exec(compile(contents+"\n", file, 'exec'), glob, loc)

  File "C:/Users/Sulod/Networks/VRPTW_GA/gavrptw/core.py", line 10, in <module>

    from . import BASE_DIR

ImportError: cannot import name 'BASE_DIR'

Process finished with exit code -1