round(<integer>, <n>) throws NotImplementedError

[dhalbert]

Reported by forum user lawrenceyy in https://forums.adafruit.com/viewtopic.php?f=60&t=151793:

round(<integer>, <n>) throws NotImplementedError. User found this via round(0, 2). round(<float>, 2) is OK, as is round(<integer>).

This was working in 3.1.2, but broke as early as 4.0.0-beta.2. MicroPython 1.9.4 seems OK.

[dhalbert]

This has to do with the default setting of MICROPY_PY_BUILTINS_ROUND_INT being 0, which was added by micropython@b318ebf. The original idea was to add handling negative rounding of integers, like round(123,-1), but it took significant extra code, so the flag was added. I'm not sure it was Damien's intention to disallow two-arg rounding of integers completely. I filed an issue there and will see what he says. In the meantime, we might turn this on, or just fix it ourselves if it grows the code too much.

[dhalbert]

@tannewt Enabling MICROPY_PY_BUILTINS_ROUND_INT adds 151 bytes to image. Fixing the code so that round(x, <negative n>) is still not implemented but `round(, ) works adds 16 bytes.

Current trinket build with French translation has 1264 bytes free with this turned on. That may be the largest one right now.

[tannewt]

I'm fine adding it back.

[dhalbert]

Fixed by #1896.