Performance boost in BaseFinderStorage.find_storage

Avoid listing all files for every finder for finding a file. This is
actually a bottleneck when the directory hierarchy is nested or the
number of files served in DEBUG mode is big. Since this flow is done in
every request, it slows down page loading.

In production environments where templates are usually cached performance
doesn't get hit by this.

pipeline/storage.py

@@ -117,11 +117,12 @@ class BaseFinderStorage(PipelineStorage):
 
     def find_storage(self, name):
         for finder in self.finders.get_finders():
-            for path, storage in finder.list([]):
-                prefix = getattr(storage, 'prefix', None)
-                matched_path = self.match_location(name, path, prefix)
-                if matched_path:
-                    return matched_path, storage
+            path = finder.find(name)
+            if path:
+                for storage_root, storage in finder.storages.items():
+                    if path.startswith(storage_root):
+                        return path, storage
+
         raise ValueError("The file '%s' could not be found with %r." % (name, self))
 
     def _open(self, name, mode="rb"):