Process aborted with BorrowMutError

[Thomasdezeeuw]

In log we borrow a RefCell and unwrap the result: https://github.com/Thomasdezeeuw/std-logger/blob/20e4307d85cd9e0c418674dab607ab33e75d9c55/src/lib.rs#L429

Somewhere in a double panic this lead to an aborted process on macOS while developing another crate. Two points to fix:

• Don't unwrap the borrow_mut call, instead create a new Buffer.
• Try to reduce the scope of the borrow of the buffer, maybe release the buffer before calling log_failure.

[Thomasdezeeuw]

This happens if a part of the log message panics. For example:

struct T;

impl fmt::Display for T {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        panic!()
    }
}

info!("T: {}", T);