Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
Rush could not get true randomness from the operating system, so it refused to make an id. Let's see why that matters. When you ask for a random id, rush draws the bytes from the operating system's own source of entropy, the one meant for security. Almost always it answers right away. This time it said no. Rush could have fallen back on something weaker, like the clock, or a simple generator, and given you an id that looks random. But a weak id is dangerous. If it can be guessed, then anything that depends on it, a session, a token, a link, can be guessed too. So id dot random is fail closed: if it cannot be sure the id is strong, it gives you no id at all. The message shows the operation and the reason from the system. This can happen in unusual environments, like a very early boot, or a restricted sandbox. Check that the system's random source is available, and try again. A missing id is better than a guessable one.
Text from the Rush engine's error catalogue.