Add unit test for utils.py

[hakanbakacak]

related #149

[mynameisvinn]

@hakanbakacak for some reason it is failing a test.

dst_url = 'snark-test/cp_copy_dataset_gcs_1a', token = None, fs = None
public = True
src_url = '/home/circleci/project/data/testing/cp_original_ds_local_3'
src_fs = <fsspec.implementations.local.LocalFileSystem object at 0x7f1808c97220>

    def _copy_helper(
        dst_url: str, token=None, fs=None, public=True, src_url=None, src_fs=None
    ):
        """Helper function for Dataset.copy"""
        src_url = src_fs.expand_path(src_url)[0]
        dst_url = dst_url[:-1] if dst_url.endswith("/") else dst_url
        dst_fs, dst_url = (
            (fs, dst_url) if fs else get_fs_and_path(dst_url, token=token, public=public)
        )
        if dst_fs.exists(dst_url) and dst_fs.ls(dst_url):
>           raise DirectoryNotEmptyException(dst_url)
E           hub.exceptions.DirectoryNotEmptyException: The destination url snark-test/cp_copy_dataset_gcs_1a for copying dataset is not empty. Delete the directory manually or use Dataset.delete if it's a Hub dataset

hub/api/dataset_utils.py:182: DirectoryNotEmptyException

[hakanbakacak]

I can't find the source of the problem. Do you have any suggestions for solving this problem?

[AbhinavTuli]

@hakanbakacak could you try merging master into your branch? I believe it should fix the issue 😄

[mynameisvinn]

@hakanbakacak This looks good! Thanks for the PR.