[BUG] Run Crash When Passing a Dictionary-Like String to ScriptRunner.script_args

[avelinoapheris]

Describe the bug
When using ScriptRunner to generate the client portion of a job, passing a string with curly brackets ({}) to script_args causes a crash. For example, if a parameter is a JSON-compatible string like "--param1={'A':1, 'B':2}" and job.simulator_run() is called, the execution fails at this line.

It appears that NVFlare interprets curly brackets as placeholders for variable substitution, even when the string should be passed as-is.

To Reproduce
A quick and dirty way to reproduce the issue is by modifying one of the example scripts, such as hello-pt.

Set script_args to a string containing curly brackets, e.g., "--data_path {}".
Run the job.

Expected behavior
The run should crash. One of the lines on the log.txt should be an error message similar to:

nvflare.fuel.common.excepts.ConfigError: Error processing '/tmp/nvflare/jobs/workdir/site-2/simulate_job/app_site-2/config/config_fed_client.json' in element '"--data_path {}"': path: 'executors.#1.executor.args.task_script_args', exception: 'IndexError: Replacement index 0 out of range for positional args tuple'

Screenshots
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Desktop (please complete the following information):

• OS: Ubuntu 22.04, macOS
• Python Version: 3.10.16
• NVFlare Version: 2.5.2