Error style

Created by: Mojo4242

Hi,

I often see some programs aborting with expect() or with an unwrap(). This makes message quite not user-friendly.

For examples:

# sudo
thread 'main' panicked at 'sudo: no command provided', rust/src/libcore/option.rs:785
Invalid opcode fault at 23:0000000000413B74
TRACE: FFFFFF400010E318
  FFFFFF400010E318: FFFFFF00001224FD
  FFFFFF400010E3C8: FFFFFF0000122401
  00000180000FF6F0: 0000000000413B69
  00000180000FF700: 00000000004065FD
  00000180000FF770: 00000000004065EF
  00000180000FF7F0: 00000000004067C3
  00000180000FF820: 00000000004064F6
  00000180000FF890: 0000000000406488
  00000180000FF8F0: 0000000000416E0E
  00000180000FF960: 0000000000416C18
  00000180000FF9D0: 0000000000401AF7
  00000180000FFDC0: 0000000000413B5C
  00000180000FFDD0: 0000000000406726
  00000180000FFE00: 000000000040E0EE
  00000180000FFE20: 0000000000406AF4
  00000180000FFE80: 000000000041A13C
 0000008000000018: EMPTY RETURN
SIGNAL 4, CPU 0, PID ContextId(41)
NAME file:/bin/sudo
Child ended by signal

The essential message here is sudo: no command provided

This lead to the question of style in error management:

1. Should we nearly banish expect() and unwrap(), manage error, print an error message to stderr and exit if appropriate ?
2. Should we abort with these function and adapt them to print a nicer output ?

I would go for 1. as it's makes safer code and when it backtrace, you know that's BAD. I would add a new line about this in rusting_properly

What do you think about that ?