formatting.hpp: szmod assert fails

[fido2020]

(In formatting.hpp, do_printf_chars)
case 'c': FRG_ASSERT(!opts.fill_zeros); FRG_ASSERT(!opts.left_justify); FRG_ASSERT(!opts.alt_conversion); ---->FRG_ASSERT(szmod == printf_size_mod::default_size); Fails when running Python 3.8