Explicitly catches and logs exceptions in creating Callback context objects. Relevant particularly if the user uses a custom class that overrides from_update. Since from_error calls from_update, exceptions in from_update can currently completely shut down update processing and error handling. See https://t.me/pythontelegrambottalk/253238 for reference.
Work in progress, e.g. tests are still missing.

interesting edge case scenario

LGTM

Bibo-Joshi deleted the error-handling-context-building branch