Not every system uses 'utf-8' as a default encoding for opening files in Python.
Before you say that there must be a way to set default encoding in one line, no, there is not. At least, I didn't found a way to do this.
The two most common reasons that `mvt-ios decrypt-backup` can fail are
wrong passwords and not pointing to an actual backup.
We can distinguish these cases based on the kinds of errors thrown
from iOSbackup (at least for the current versions that i'm testing
with).
When we encounter those particular exceptions, just report a simple
summary and don't overwhelm the user with a backtrace. If we
encounter an unexpected exception, leave the reporting as-is.
Closes: #28, #36
