...

src/calibre/library/cli.py

@@ -47,6 +47,9 @@ def get_parser(usage):
 def get_db(dbpath, options):
     if options.library_path is not None:
         dbpath = options.library_path
+    if dbpath is None:
+        raise ValueError('No saved library path, either run the GUI or use the'
+                ' --with-library option')
     dbpath = os.path.abspath(dbpath)
     return LibraryDatabase2(dbpath)