Improve error message when required argument is missing

[markrahimi]

Description

When a required function argument is not provided via the command line, Python Fire raises a generic TypeError that doesn't clearly indicate which argument is missing or how to provide it.

Current Behavior

$ python my_script.py greet
TypeError: greet() missing 1 required positional argument: 'name'

Expected Behavior

A more user-friendly error message that would guide the user:

$ python my_script.py greet
Error: Missing required argument 'name'
Usage: my_script.py greet <name>

Motivation

This would significantly improve the user experience, especially for new users who are unfamiliar with Python tracebacks. Clear error messages are crucial for CLI tools.

Environment

• Python Fire version: 0.7.1
• Python version: 3.11
• OS: macOS

Possible Solution

Catch TypeError exceptions in the argument parsing logic and check if they're related to missing arguments, then provide a more descriptive message with usage hints.

[saivedant169]

Taking this on. The main missing-argument case is already caught by _ParseArgs (raises FireError with a descriptive message). But there are edge cases where TypeError from the actual fn(*varargs, **kwargs) call slips through uncaught — these crash with a raw Python traceback instead of the nice Fire error format.

The fix wraps the function call in _CallAndUpdateTrace with a try/except that converts argument-related TypeError to FireError, so they flow through Fire's error display pipeline (error message + usage text). All 91 existing tests pass.

PR incoming.