[IMPROV] Reduce usage of unicode()

The unicode() builtin is not necessary if it's added unmodified via
format or %-notation into a unicode string (e.g. u'{0}'.format(value)).

In addition, the localized time formatting was removed. The default
'C' locale (which is ASCII by definition) is now used instead.

Change-Id: I77017db516e6573ce463628167e9c4f2cf845aab