private function validate_upload( $file ) {

		if ( ! empty( $file['error'] ) ) {

			switch ( $file['error'] ) {

				case UPLOAD_ERR_INI_SIZE:
					$msg = __( 'The uploaded file exceeds the upload_max_filesize directive in php.ini.', 'lifterlms' );
					break;

				case UPLOAD_ERR_FORM_SIZE:
					$msg = __( 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.', 'lifterlms' );
					break;

				case UPLOAD_ERR_PARTIAL:
					$msg = __( 'The uploaded file was only partially uploaded.', 'lifterlms' );
					break;

				case UPLOAD_ERR_NO_FILE:
					$msg = __( 'No file was uploaded.', 'lifterlms' );
					break;

				case UPLOAD_ERR_NO_TMP_DIR:
					$msg = __( 'Missing a temporary folder.', 'lifterlms' );
					break;

				case UPLOAD_ERR_CANT_WRITE:
					$msg = __( 'Failed to write file to disk.', 'lifterlms' );
					break;

				case UPLOAD_ERR_EXTENSION:
					$msg = __( 'File upload stopped by extension.', 'lifterlms' );
					break;

				default:
					$msg = __( 'Unknown upload error.', 'lifterlms' );

			}
		} else {

			$info = pathinfo( $file['name'] );

			if ( 'json' !== strtolower( $info['extension'] ) ) {
				$msg = __( 'Only valid JSON files can be imported.', 'lifterlms' );
			}
		}

		if ( ! empty( $msg ) ) {
			return new WP_Error( 'llms_import_file_error', $msg );
		}

		return true;

	}