remote add: does not fail in non-DVC repo

[shcheklein]

Version:

WARNING: Unable to detect supported link types, as cache directory '.dvc/cache' doesn't exist. It is usually auto-created by commands such as `dvc add/fetch/pull/run/import`, but you could create it manually to enable this check.
DVC version: 0.81.3+7f5e4a
Python version: 3.7.5
Platform: Darwin-18.2.0-x86_64-i386-64bit
Binary: False
Package: None

Reproduce:

mkdir project
cd project
dvc remote add storage gdrive://root/storage

should probably fail.

next command fails:

dvc remote modify storage gdrive_client_id test
ERROR: configuration error - config file error: unable to find remote section 'storage'

message should be different - no config file, or repo is not DVC, etc.

Closing, duplicate of #2309

ohhh, my bad @shcheklein, definitely related but this is about add, mine was about modify.

Anyways, I think both add and modify should fail if --global or --system is not specified.

[efiop]

Closing in favor #2309