The error message "No such user: username" typically indicates that a program or script is trying to perform an operation involving a user account that doesn't exist on the system. This can happen in both Node.js and Python applications.

Here are some steps you can take to troubleshoot this issue:

1. Check if the username exists: Make sure that the username you're trying to use actually exists on the system. In Linux, you can use the cat /etc/passwd command to list all users.

2. Ensure correct username format: Ensure that you are providing the username in the correct format. Usernames are case-sensitive in most systems, so make sure you're using the correct capitalization.

3. Permissions: Check if the user running the script has the necessary permissions to access or modify user information. In some cases, you might need to run the script with elevated privileges (using sudo in Linux).

4. Error Handling: Wrap the code that's interacting with user accounts in a try-catch block to handle potential exceptions or errors gracefully. This way, you can provide a more meaningful error message to the user or log the error for later analysis.

5. Check system logs: Check system logs (e.g., /var/log/auth.log in Linux) for any relevant error messages. It might provide additional information about why the user is not found.

6. Debugging with print statements: Insert print statements in your code to help identify where exactly the error is occurring. Print out the username before you attempt to perform any operations on it.

7. Environment Differences: Ensure that the environment in which you are running the script (development vs. production, different machines) has the same user setup.

8. Verify input data: If the username is coming from user input, make sure it's properly sanitized and validated to prevent any potential issues.

Without more context about the specific code you're running and the system/environment you're in, it's hard to provide a more specific solution. If you can provide more details about your code and the environment you're running it in, I'd be happy to offer more tailored advice.