It's a waste to lose the entire staging if it's only a short blip /
delay thing, so retry multiple times. Add utility function to make
backoff functions easier (though the UI is not great ATM).
Also log the "left" parent of a merge commit (which should be the
"base") when creating it, for additional post-mortem information.
Github is subject to a fair amount of transient failures, which are
currently ill-logged: an exception is raised and the caller /
responsible might eventually log something, but it's not really
formalised and centralised, and is thus inconvenient to try and
post-mortem issues with github's support.
Change this such that *almost* all github API calls get extensively
logged (status, reason, all headers, body) on failure.
Also automatically sets debug logging for odoo in local tests, and
alter the fake response constructor thing so it doesn't set a json
mimetype when the body is not valid json.
Closes#98
