push: improve 'no remote specified' hint

Fixes #3121

dvc/config.py

@@ -24,13 +24,21 @@ class ConfigError(DvcException):
 
 
 class NoRemoteError(ConfigError):
-    def __init__(self, command):
-        msg = (
-            "no remote specified. Setup default remote with\n"
-            "    dvc remote default <name>\n"
-            "or use:\n"
-            "    dvc {} -r <name>\n".format(command)
-        )
+    def __init__(self, command, *, has_any_remote=True):
+        if has_any_remote:
+            msg = (
+                "no remote specified. Setup default remote with\n"
+                "    dvc remote default <remote name>\n"
+                "or use:\n"
+                "    dvc {} -r <remote name>".format(command)
+            )
+        else:
+            msg = (
+                "no remote specified. Create a remote with\n"
+                "    dvc remote add <remote name> <remote url>\n"
+                "To create a default remote use the -d flag:\n"
+                "    dvc remote add -d <remote name> <remote url>\n"
+            )
 
         super().__init__(msg)
 

dvc/data_cloud.py

@@ -39,7 +39,9 @@ class DataCloud(object):
         if remote:
             return self._init_remote(remote)
 
-        raise NoRemoteError(command)
+        has_any_remote = any(key.startswith("remote ") for key in self._config)
+
+        raise NoRemoteError(command, has_any_remote=has_any_remote)
 
     def _init_remote(self, remote):
         return Remote(self.repo, name=remote)