MICROPY_PY_BUILTINS_ROUND_INT==0 breaks round(<int>, <n>)
Before https://github.com/micropython/micropython/commit/b318ebf1015ced6354f8bbaf035308214b3f5c5d, which was a rework of #3557, round(<int>, <n>) worked. Now, if MICROPY_PY_BUILTINS_ROUND_INT is set to 0, round(2, 2) or similar throws NotImplementedError. round(2) still works.
@dpgeorge Was it your intention to disable rounding of integers in this way completely, instead of just not handling negative values for the second arg if it was an int?
A user discovered this after ending up with an integer zero while doing some floating arithmetic.
Problem with round on esp8266
MicroPython v1.8.7-623-g209eaec-dirty on 2017-04-15; ESP module with ESP8266
I haven't figured out the pattern (since some results are correct) but there appears to be a problem with round.
round(0.55, 1)
0.5
round(0.56, 1)
0.5999999