dvc: use ' for dynamic output and ` for DVC names (follow-up)

continues https://github.com/iterative/dvc/pull/2644#discussion_r338417698

dvc/analytics.py

@@ -164,4 +164,4 @@ def _find_or_create_user_id():
             return user_id
 
     except LockError:
-        logger.debug("Failed to acquire {lockfile}".format(lockfile=lockfile))
+        logger.debug("Failed to acquire '{lockfile}'".format(lockfile=lockfile))

dvc/command/diff.py

@@ -31,7 +31,7 @@ class CmdDiff(CmdBase):
     def _get_md5_string(sign, file_name, checksum):
         sample_msg = ""
         if file_name:
-            sample_msg = "{}{} with md5 {}\n"
+            sample_msg = "'{}{}' with md5 {}\n"
             sample_msg = sample_msg.format(sign, file_name, checksum)
         return sample_msg
 

dvc/command/imp_url.py

@@ -19,7 +19,7 @@ class CmdImportUrl(CmdBase):
             )
         except DvcException:
             logger.exception(
-                "failed to import {}. You could also try downloading "
+                "failed to import '{}'. You could also try downloading "
                 "it manually, and adding it with `dvc add`.".format(
                     self.args.url
                 )