Improve stack traces?

[ivnsch]

We got a panic in the iOS app:

2020-05-27 16:32:00.595290+0200 CoEpi[17572:301644] [AppCenter] WARNING: +[MSKeychainUtil stringForKey:withServiceName:statusCode:]/84 Failed to retrieve item with key='MSUpdateToken', service='org.coepi.ios.AppCenter' from keychain. OS Status code -25300
2020-05-27 16:32:00.606387+0200 CoEpi[17572:301644] [services] Updating app badge: 0
R Start matching...
thread '<unnamed>' panicked at 'index 24 out of range for slice of length 16', src/libcore/slice/mod.rs:2725:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
libc++abi.dylib: terminating with uncaught foreign exception

The message says

run with `RUST_BACKTRACE=1` environment variable to display a backtrace`

Where do we set this?

[duskoo]

@i-schuetz I assume that would be env variable on the OS/machine which is executing the Rust code. I doubt it can help us debug a compiled lib running on iOS.

1. Can we reproduce the issue on development machine somehow?
2. Can we reproduce the issue with debug build of the library?

[duskoo]

iOS 76eef12 and Rust 345c4a0 -> no crash

[ivnsch]

The issue to track the specific crash is #23
This is only to improve the stack traces in general.