Get rid of codecs.open()

[sebastian]

Background

codecs.open() has been superseded by io.open(). Beside beeing newer, io.open() if used in text mode, also enforces the written data to be unicode objects, preventing accidental encoding issues.

Moreover, some code currently uses codecs.open() while binary data actually sent or expected. That code will currently result in encoding errors when encountering non-ASCII characters.

What to change

Replace codecs.open() with io.open() when processing decoded text, and otherwise with open().

[sebastian]

My assumptions here weren't quite right. Though using io.open() instead makes sense for new code, but this isn't worth changing the existing code. The prospect of breaking something and the afford properly testing the change would be too large.