CLI command crashes with unhandled FileNotFoundError when input file does not exist

[sowjanyakb]

Description

Several CLI commands do not validate whether the provided input file exists before attempting to open it.

Running commands with a non-existent file causes an unhandled exception and displays a raw Python traceback instead of a user-friendly error message.

Root Cause Analysis

The CLI directly attempts to open the provided file path without checking whether the file exists or handling FileNotFoundError.

Because of this, exceptions propagate to the terminal and crash the command execution.

[jmestwa-coder]

@sowjanyakb

Could you please share:

• the exact command used
• the full traceback/output
• which CLI commands are affected
• what behavior you expect instead

I’d also like to confirm whether this should be handled locally by each command or through centralized CLI error handling before moving toward a fix.

[sowjanyakb]

Command used:
sigflow replay nonexistent.tlv

Observed output:
Traceback (most recent call last):
File "...", line ...
FileNotFoundError: [Errno 2] No such file or directory: 'nonexistent.tlv'

Affected CLI commands:

• sigflow replay
• potentially other commands that accept file input paths without validation

Expected behavior:
Instead of displaying a raw Python traceback, the CLI should gracefully handle missing files and return a user-friendly error such as:

Error: input file 'nonexistent.tlv' does not exist

Suggested handling:
A centralized CLI-level validation/error handling approach may be preferable since multiple commands appear to rely on file inputs. This would avoid duplicated validation logic across commands and ensure consistent error reporting throughout the CLI.

Possible implementation:

if not os.path.exists(path):
raise click.BadParameter(f"Input file '{path}' does not exist")