api: throw exception by get_url if not a dvc repo

dvc/api.py

@@ -10,7 +10,7 @@ import ruamel.yaml
 from voluptuous import Schema, Required, Invalid
 
 from dvc.repo import Repo
-from dvc.exceptions import DvcException
+from dvc.exceptions import DvcException, NotDvcRepoError
 from dvc.external_repo import external_repo
 
 
@@ -43,13 +43,27 @@ class SummonError(DvcException):
     pass
 
 
+class UrlNotDvcRepoError(DvcException):
+    """Thrown if given url is not a DVC repository.
+
+    Args:
+        url (str): url to the repository.
+    """
+
+    def __init__(self, url):
+        super().__init__("URL '{}' is not a dvc repository.".format(url))
+
+
 def get_url(path, repo=None, rev=None, remote=None):
     """Returns an url of a resource specified by path in repo"""
-    with _make_repo(repo, rev=rev) as _repo:
-        abspath = os.path.join(_repo.root_dir, path)
-        out, = _repo.find_outs_by_path(abspath)
-        remote_obj = _repo.cloud.get_remote(remote)
-        return str(remote_obj.checksum_to_path_info(out.checksum))
+    try:
+        with _make_repo(repo, rev=rev) as _repo:
+            abspath = os.path.join(_repo.root_dir, path)
+            out, = _repo.find_outs_by_path(abspath)
+            remote_obj = _repo.cloud.get_remote(remote)
+            return str(remote_obj.checksum_to_path_info(out.checksum))
+    except NotDvcRepoError:
+        raise UrlNotDvcRepoError(repo)
 
 
 def open(path, repo=None, rev=None, remote=None, mode="r", encoding=None):