# Buggy code
def fetch_external(self, paths: Iterable, **kwargs):
    """Fetch specified external repo paths into cache.

    Returns 3-tuple in the form
        (downloaded, failed, list(cache_infos))
    where cache_infos can be used as checkout targets for the
    fetched paths.
    """
    download_results = []
    failed = 0

    paths = [PathInfo(self.root_dir) / path for path in paths]

    def download_update(result):
        download_results.append(result)

    save_infos = []
    for path in paths:
        if not self.repo_tree.exists(path):
            raise PathMissingError(path, self.url)
        hash_info = self.repo_tree.save_info(path, download_callback=download_update)
        self.local_cache.save(
            path,
            self.repo_tree,
            hash_info,
            save_link=False,
            download_callback=download_update,
        )
        save_infos.append(hash_info)

    return sum(download_results), failed, save_infos


# Traceback (dvc.exceptions.RemoteCacheRequiredError)
2020-07-01 17:14:02,947 DEBUG: fetched: [(3,)]
2020-07-01 17:14:03,123 DEBUG: Removing output 'some_target' of stage: 'some_target.dvc'.
Importing 's3://some_bucket/some_target' -> 'some_target'
2020-07-01 17:14:03,123 DEBUG: Computed stage: 'some_target.dvc' md5: '2f8b87d3b22efd1638f414c3b3f65614'
2020-07-01 17:14:03,123 DEBUG: 'md5' of stage: 'some_target.dvc' changed.
2020-07-01 17:14:04,088 DEBUG: fetched: [(0,)]
2020-07-01 17:14:04,146 ERROR: failed to import s3://some_bucket/some_target. You could also try downloading it manually, and adding it with `dvc add`. - Current operation was unsuccessful because 's3://some_bucket/some_target' requires existing cache on 's3' remote. See <https://man.dvc.org/config#cache> for information on how to set up remote cache.
------------------------------------------------------------
Traceback (most recent call last):
File "/usr/lib/python3.8/site-packages/dvc/command/imp_url.py", line 14, in run
self.repo.imp_url(
File "/usr/lib/python3.8/site-packages/dvc/repo/__init__.py", line 36, in wrapper
ret = f(repo, *args, **kwargs)
File "/usr/lib/python3.8/site-packages/dvc/repo/scm_context.py", line 4, in run
result = method(repo, *args, **kw)
File "/usr/lib/python3.8/site-packages/dvc/repo/imp_url.py", line 54, in imp_url
stage.run()
File "/home/anotherbugmaster/.local/lib/python3.8/site-packages/funcy/decorators.py", line 39, in wrapper
return deco(call, *dargs, **dkwargs)
File "/usr/lib/python3.8/site-packages/dvc/stage/decorators.py", line 35, in rwlocked
return call()
File "/home/anotherbugmaster/.local/lib/python3.8/site-packages/funcy/decorators.py", line 60, in __call__
return self._func(*self._args, **self._kwargs)
File "/usr/lib/python3.8/site-packages/dvc/stage/__init__.py", line 424, in run
sync_import(self, dry, force)
File "/usr/lib/python3.8/site-packages/dvc/stage/imports.py", line 29, in sync_import
stage.save_deps()
File "/usr/lib/python3.8/site-packages/dvc/stage/__init__.py", line 387, in save_deps
dep.save()
File "/usr/lib/python3.8/site-packages/dvc/output/base.py", line 268, in save
self.info = self.save_info()
File "/usr/lib/python3.8/site-packages/dvc/output/base.py", line 192, in save_info
return self.remote.save_info(self.path_info)
File "/usr/lib/python3.8/site-packages/dvc/remote/base.py", line 762, in save_info
return self.tree.save_info(path_info, **kwargs)
File "/usr/lib/python3.8/site-packages/dvc/remote/base.py", line 329, in save_info
self.PARAM_CHECKSUM: self.get_hash(path_info, tree=tree, **kwargs)
File "/usr/lib/python3.8/site-packages/dvc/remote/base.py", line 297, in get_hash
hash_ = self.get_dir_hash(path_info, tree, **kwargs)
File "/usr/lib/python3.8/site-packages/dvc/remote/base.py", line 311, in get_dir_hash
raise RemoteCacheRequiredError(path_info)
dvc.exceptions.RemoteCacheRequiredError: Current operation was unsuccessful because 's3://some_bucket/some_target' requires existing cache on 's3' remote. See <https://man.dvc.org/config#cache> for information on how to set up remote cache.
------------------------------------------------------------

Having any troubles? Hit us up at https://dvc.org/support, we are always happy to help!

# Fixed code
def fetch_external(self, paths: Iterable, **kwargs):
    """Fetch specified external repo paths into cache.

    Returns 3-tuple in the form
        (downloaded, failed, list(cache_infos))
    where cache_infos can be used as checkout targets for the
    fetched paths.
    """
    download_results = []
    failed = 0

    paths = [PathInfo(self.root_dir) / path for path in paths]

    def download_update(result):
        download_results.append(result)

    hash_infos = []
    for path in paths:
        if not self.repo_tree.exists(path):
            raise PathMissingError(path, self.url)
        hash_info = self.repo_tree.get_hash(
            path, download_callback=download_update
        ).to_dict()
        self.local_cache.save(
            path,
            self.repo_tree,
            hash_info,
            save_link=False,
            download_callback=download_update,
        )
        hash_infos.append(hash_info)

    return sum(download_results), failed, hash_infos