Improve error handling

[tchapacan]

Error handling has been naively implemented as it is in early stage. Some error can throw a panic (and they might shouldn't?) vs other no (and they should?)

A revisit of the case where error handling is messy and refacto/take appropriate decision where it is necessary.

Here some documentation related to error handling in rustbook : https://doc.rust-lang.org/book/ch09-03-to-panic-or-not-to-panic.html