CLI: change return output for 'checkout' and 'pull' commands

Change messages output after return of some commands:

* Remove warning for 'dvc checkout' & commands calling it under the hood
* Add an informational message output for 'dvc pull' command

Fixes #2685.

dvc/repo/checkout.py

@@ -50,12 +50,6 @@ def _checkout(
         total=total, unit="file", desc="Checkout", disable=total == 0
     ) as pbar:
         for stage in stages:
-            if stage.locked:
-                logger.warning(
-                    "DVC-file '{path}' is locked. Its dependencies are"
-                    " not going to be checked out.".format(path=stage.relpath)
-                )
-
             failed.extend(
                 stage.checkout(force=force, progress_callback=pbar.update_desc)
             )

dvc/repo/pull.py

@@ -1,6 +1,11 @@
 from __future__ import unicode_literals
 
-from . import locked
+import logging
+
+from dvc.repo import locked
+
+
+logger = logging.getLogger(__name__)
 
 
 @locked
@@ -20,11 +25,16 @@ def pull(
         jobs,
         remote=remote,
         all_branches=all_branches,
-        all_tags=all_tags,
         with_deps=with_deps,
+        all_tags=all_tags,
         recursive=recursive,
     )
     self._checkout(
-        targets=targets, with_deps=with_deps, force=force, recursive=recursive
+        targets=targets,
+        with_deps=with_deps,
+        force=force,
+        recursive=recursive,
+
     )
+    logger.info("Data retrieved successfully from DVC remote storage.")
     return processed_files_count