dvc: missing caches and DownloadError

[Suor]

Missing caches yields a warning while any other error leading to partial fetch leads to DownloadError. This discrepancy will cause issues, e.g. with CheckoutError later.

An example would be this test:
https://github.com/iterative/dvc/blob/156fc9d4e1b438a5b9766a343af090f8bd22385c/tests/func/test_import.py#L67-L81

If we repalce shutil.rmtree(erepo.root_dir) with shutil.rmtree(erepo.dvc.cache.local.cache_dir), then suddenly we don't have DownloadError anymore it's CheckoutError, but maybe that test is just bad.

[efiop]

@Suor Are you sure this happens on master and not in your caching patch?

[Suor]

The issue is that missing caches is not an error, in master, it never was. This made some sense while we were ignoring download errors also, but it's an incoherency now, which will cause issues.

[Suor]

This is related to #2608

[dmpetrov]

@Suor was this issue resolved by #2608?

[Suor]

@dmpetrov No, that PR was not solving this and it was closed not merged.

[skshetry]

Closing as stale.