When I try to run the following

def test(fmt, *args):
    print(fmt.format(*args))
test('{}', 1)

I get:

2121 >./micropython x.py
code 0x1bff006, byte code 0x97 not implemented
micropython: ../py/vm.c:636: mp_execute_byte_code_2: Assertion `0' failed.
Aborted

This appears to be from the fmt.format

I was trying to write some tests for str.format and be able to wrap an exception handler around the tests so that I could report the exception thrown from malformed format strings.

I'll switch back to the original style for the time being.