py3: use "%f" for formatting floating point number

py3: fix progress() functions to not use "%s" with int Python3 doesn't support "%s" with int arguments (and not with None arguments either, which this code was also using).

py3: make random topic name generation consistent across py2/py3 random.choice() (and others based on random.randint()) changed between py2 and py3 without a way to get the py2 behavior. However, random.random() did not change, so we can re-implement random.choice() based on that.

py3: convert str to bytes before passing to core exception

py3: convert opts keys to bytes before passing to core APIs

evolve: further clarify when update is performed

py3: avoid comparing int and None

py3: avoid "%r" for list of byte strings, which produces b'' on py3

py3: avoid "%r" for byte string, which produces b'' on py3 Replaced by "'%s'", which I think is clearer anyway.

py3: replace str(ctx) by bytes(ctx) These are all for messages to the user and we don't want unicode for that.

py3: use inspect.signature() instead of inspect.getargspec() on py3

py3: use array.array.{to,from}bytes() on py3 array.array.{to,from}string() still exists on py3, but they're deprecated and generate warnings. I've put the compat function in compat.pt for now. We can move into a dedicated pycompat.py if we end up with a lot of py3 compat stuff.

py3: config values can be bytes, but never unicode

py3: call branchmap.items() on py3 and continue to call iteritems() on py2 Mercurial's source transformer also replaces the 'def iteritems(' in branchmap by 'def items(', so we need to call whichever version is there.