OperationalError: (OperationalError) unable to open database file None None

I had the same problem in windows 8.1. Based on sqlalchemy documentation:

sqlite:////db_absolute_path

sqlite:///db_relative_path

(notice that the second line above has only 3 slashes) In my case providing relative path helped.

After reading the docs on sqlite urls here, I decided you have the right number of slashes. Apparently, it uses the same parser to pull out the path as the remote connection engines, so the "server name" that would go between the second and third slash is left blank.

If you want to specify an absolute path, you are going about it the right way. Check to be sure you are providing an absolute path. Three slashes may be able to specify a relative path, but you need to know the current working directory of your app, which might break when you delay your app.

You mention that it is a path to user tyre77 on OS X, so shouldn't that be sqlite:////Users/tyre77/OmniCloud/database.db?

Also, three slashes for relative paths, four for absolute paths.