Python 3 refinements in the COBE codebase

[wallabra]

Given that COBE has just finished its transition to the world of Python 3 (and welcome, by the way! :D), there are still, inevitably, some rough spots here and there.

This issue seeks to coordinate and group any of my smaller contributions meant to help COBE perform better in the world of Python 3, as well as serve as a little list of the things I actually did in it.

Since each pull request wouldb e a batch of little changes, each almost indistinguishable from the one before and the one after, try keeping relevant discussion to this issue :)

Ahh, if only we could split an issue's discussion into multiple threads.

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Changes:

• c01 - Avoid using str.encode(....) where it is unnecessary: Most Python 3 libraries and functions accept str, unless they specifically do bytewise or binary operation, such as manipulating raw data (like base64) or reading a struct (like, well, `struct').

PRs:

None yet. See https://github.com/Gustavo6046/cobe/tree/py3-refinement