chat: set AttachmentImageItem in python instead of kv: "source" is a StringProperty, and setting it in kv was in some case resulting in a "None" set, which was leading to a crash when Kivy cache was purged. It is now set in Python to avoid this problem.

[DEFAULT]
bridge = pb
log_level = debug
log_fmt = #[%%(levelname)s][%%(name)s] %%(message)s

[cagou]
no_certificate_validation = true
log_level = debug
log_fmt = [%%(levelname)s][%%(name)s] %%(message)s