Parse default remote properly

[dmpetrov]

Currently, the remote type is checked in a not consistent way by finding string patterns like s3:// in dvc remote list outputs. That might be a problem when multiple remotes are defined.

In fact, dvc remote default returns the default remote name which can be properly resolved to URL in the dvc remote list output by a simple pattern.

Also, it makes sense to throw an error and exit with a proper message if dvc pull is required but the corresponded setting are not.

[DavidGOrtega]

dvc-cml should not be handling this anymore, aside the exceptions like gs and ssh.
The code does nothing but warn so its removed in next PR delegating the responsibility to DVC.
In the case of gs and ssh it has to transform the json content inside the env variable into a file that gs is looking for. Something similar in ssh, the given key has to be added.

[dmpetrov]

@DavidGOrtega you should not warn users if settings are not defined for a not default remote.

[dmpetrov]

This is how you can get the default remote from bash

dvc remote list | grep "^`dvc remote default`\t" | awk '{print($2)}'

[DavidGOrtega]

Thats what Im saying. DVC-CML only needs to interface the secrets to the runner in case it has to do it.
Right now that only happens in gs and ssh.
For the rest the whole code is removed delegating it to dvc

[dmpetrov]

Log:

Fetch all history for all tags and branches
Setting DVC remote ...
S3 DVC remote found but no credentials found
Pulling from DVC remote ...
Failed pulling from DVC remote
Error: Command failed: dvc pull -f
Running dvc repro Dvcfile
ERROR: unexpected error - Unable to locate credentials

    at ChildProcess.exithandler (child_process.js:303:12)
    at ChildProcess.emit (events.js:310:20)
    at maybeClose (internal/child_process.js:1021:16)
    at Socket.<anonymous> (internal/child_process.js:443:11)
    at Socket.emit (events.js:310:20)
    at Pipe.<anonymous> (net.js:672:12) {
  killed: false,
  code: 255,
  signal: null,
  cmd: 'dvc pull -f'
}
##[error]Command failed: dvc repro Dvcfile            <--- THIS IS IN RED
WARNING: Dependency 'train.py' of 'Dvcfile' changed because it is 'modified'.
WARNING: Stage 'Dvcfile' changed.
.... [CONTINUE SOME PROCESS]

How the log ideally should look like:

Fetch all history for all tags and branches
Setting DVC remote ...
S3 DVC remote found but no credentials found
Pulling from DVC remote ...
Failed pulling from DVC remote
Error: Command failed: dvc pull -f
Running dvc repro Dvcfile
ERROR: unexpected error - Unable to locate credentials   <--- THIS IS IN RED
[EXIT NOW - NO REASON TO CONTINUE]
##[error]Process completed with exit code 1.               <--- THIS IS IN RED 

[DavidGOrtega]

[EXIT NOW - NO REASON TO CONTINUE]
Its something that you have added right?

[dmpetrov]

@DavidGOrtega yes