base.py

    def get_filename(self, basename):
        # first try to find it with staticfiles (in debug mode)
        filename = None
        if self.storage.exists(basename):
            try:
                filename = self.storage.path(basename)
            except NotImplementedError:
                local_storage = get_storage_class('compressor.storage.CompressorFileStorage')()
                filename = local_storage.path(basename)
        # secondly try finding the file in the root
        elif self.finders:
            filename = self.finders.find(basename)
        if filename:
            return filename
        # or just raise an exception as the last resort
        raise UncompressableFileError(
            "'%s' could not be found in the COMPRESS_ROOT '%s'%s" %
            (basename, settings.COMPRESS_ROOT,
             self.finders and " or with staticfiles." or "."))