cache: Do not raise error when there are no files to remove

Instead log a warning and continue (to log that we removed 0 files)

Author: Noah Gorny

news/10459.feature.rst

@@ -0,0 +1,2 @@
+Do not raise error when there are no files to remove with ``pip cache purge/remove``.
+Instead log a warning and continue (to log that we removed 0 files).

src/pip/_internal/commands/cache.py

@@ -175,7 +175,7 @@ def remove_cache_items(self, options: Values, args: List[Any]) -> None:
             files += self._find_http_files(options)
 
         if not files:
-            raise CommandError("No matching packages")
+            logger.warning("No matching packages")
 
         for filename in files:
             os.unlink(filename)