Expand description
Assert a command stderr string is equal to an expression.
Pseudocode:
(command ⇒ stderr ⇒ string) = (expr into string)
§Example
use std::process::Command;
let mut command = Command::new("bin/printf-stderr");
command.args(["%s", "hello"]);
let s = String::from("hello");
assert_command_stderr_eq_expr!(command, s);