# Buggy code
def _get_gitignore(self, path, ignore_file_dir=None):
    if not ignore_file_dir:
        ignore_file_dir = os.path.dirname(os.path.realpath(path))

    assert os.path.isabs(path)
    assert os.path.isabs(ignore_file_dir)

    if not path.startswith(ignore_file_dir):
        msg = (
            "{} file has to be located in one of '{}' subdirectories, not outside '{}'"
        )
        raise FileNotInTargetSubdirError(
            msg.format(self.GITIGNORE, path, ignore_file_dir)
        )

    entry = os.path.relpath(path, ignore_file_dir).replace(os.sep, "/")
    # NOTE: using '/' prefix to make path unambiguous
    if len(entry) > 0 and entry[0] != "/":
        entry = "/" + entry

    gitignore = os.path.join(ignore_file_dir, self.GITIGNORE)

    if not gitignore.startswith(os.path.realpath(self.root_dir)):
        raise FileNotInRepoError(path)

    return entry, gitignore


# Traceback (ValueError)
ERROR: failed to pull data from the cloud - path is on mount 'F:', start on mount 'C:'
Traceback (most recent call last):
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\command\data_sync.py", line 46, in
do_run recursive=self.args.recursive,
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\repo\pull.py", line 24, in pull
recursive=recursive,
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\repo\fetch.py", line 27, in fetch
used, jobs, remote=remote, show_checksums=show_checksums
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\data_cloud.py", line 144, in pull
show_checksums=show_checksums,
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 493, in pull
download=True,
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 459, in _process
download=download,
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 358, in status
local_exists = self.cache_exists(md5s)
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 232, in cache_exists
return list(filter(lambda md5: not self.changed_cache_file(md5), md5s))
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 232, in <lambda>
return list(filter(lambda md5: not self.changed_cache_file(md5), md5s))
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\base.py", line 518, in changed_cache_file
actual = self.get_checksum(cache_info)
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\base.py", line 275, in get_checksum
checksum = self.get_file_checksum(path_info)
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\remote\local\__init__.py", line 208, in get_file_checksum
return file_md5(path_info.path)[0]
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\site-packages\dvc\utils\__init__.py", line 48, in file_md5                      logger.info(msg.format(os.path.relpath(fname)))
File "c:\users\srg\appdata\local\continuum\anaconda3\envs\tf-keras\lib\ntpath.py", line 584, in relpath
path_drive, start_drive))                                                                                                                        ValueError: path is on mount 'F:', start on mount 'C:'

# Fixed code
def _get_gitignore(self, path, ignore_file_dir=None):
    if not ignore_file_dir:
        ignore_file_dir = os.path.dirname(os.path.realpath(path))

    assert os.path.isabs(path)
    assert os.path.isabs(ignore_file_dir)

    if not path.startswith(ignore_file_dir):
        msg = (
            "{} file has to be located in one of '{}' subdirectories, not outside '{}'"
        )
        raise FileNotInTargetSubdirError(
            msg.format(self.GITIGNORE, path, ignore_file_dir)
        )

    entry = relpath(path, ignore_file_dir).replace(os.sep, "/")
    # NOTE: using '/' prefix to make path unambiguous
    if len(entry) > 0 and entry[0] != "/":
        entry = "/" + entry

    gitignore = os.path.join(ignore_file_dir, self.GITIGNORE)

    if not gitignore.startswith(os.path.realpath(self.root_dir)):
        raise FileNotInRepoError(path)

    return entry, gitignore