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

@@ -170,12 +170,16 @@ def remove_cache_items(self, options: Values, args: List[Any]) -> None:
 
         files = self._find_wheels(options, args[0])
 
-        # Only fetch http files if no specific pattern given
+        no_matching_msg = "No matching packages"
         if args[0] == "*":
+            # Only fetch http files if no specific pattern given
             files += self._find_http_files(options)
+        else:
+            # Add the pattern to the log message
+            no_matching_msg += ' for pattern "{}"'.format(args[0])
 
         if not files:
-            raise CommandError("No matching packages")
+            logger.warning(no_matching_msg)
 
         for filename in files:
             os.unlink(filename)