while running YOLO for test custom object cfg file path error the path is correct but even though its showing this error
Oftenly I was also used  get something similar to this error 
my first mistake was not to open Jupyter notebook at the directory where I kept these folders
so, try to open the notebook from that directory 
(in windows simply type cmd on location bar of shift+right-click)
(in MacOS there is some setting first enable that then right-click on the folder)
later I used this options 
options={
    'model':'cfg/yolo.cfg',
    'load':'bin/yolov2.weights',
    'threshold':0.3,
    'gpu':1.0
}
tfNet=TFNet(options)
and everything work as expected
hope this will help you
This code is for running my trained weights the folder ckpt contains 1050 step train data and this file is in outside of cfg folder in darkflow main folder.
import cv2
from darkflow.net.build import TFNet
import numpy as np
import time
options = {
    'model': 'cfg/tiny-yolo-voc-1c.cfg',
    'load': 1050,
    'threshold': 0.2,
    'gpu': 1.0
}
after running this code in atom editor below error showing
Parsing cfg//tiny-yolo-voc-1c.cfg
Traceback (most recent call last):
  File "C:\Users\amard\Desktop\Hotel\darkflow\test.py", line 13, in <module>
    tfnet = TFNet(options)
  File "C:\Users\amard\Desktop\Hotel\darkflow\darkflow\net\build.py", line 58, in __init__
    darknet = Darknet(FLAGS)
  File "C:\Users\amard\Desktop\Hotel\darkflow\darkflow\dark\darknet.py", line 17, in __init__
    src_parsed = self.parse_cfg(self.src_cfg, FLAGS)
  File "C:\Users\amard\Desktop\Hotel\darkflow\darkflow\dark\darknet.py", line 68, in parse_cfg
    for i, info in enumerate(cfg_layers):
  File "C:\Users\amard\Desktop\Hotel\darkflow\darkflow\utils\process.py", line 66, in cfg_yielder
    layers, meta = parser(model); yield meta;
  File "C:\Users\amard\Desktop\Hotel\darkflow\darkflow\utils\process.py", line 17, in parser
    with open(model, 'rb') as f:
FileNotFoundError: [Errno 2] No such file or directory: 'cfg//tiny-yolo-voc-1c.cfg'
[Finished in 4.298s]