"const" was never a keyword in the strict sense of the lexer (eg "for" is a keyword). The recent changes to "const" usage are the following:
- micropython.const(x) function was added, which just returns its argument.
- all Python scripts in the micropython repository that use the const feature had "from micropython import const" added to them.
The reason is to make this const feature compatible with CPython, if you have a dummy micropython module with a dummy const function.
Old scripts will continue to work just fine, the "from micropython import const" is not strictly necessary, but highly recommended for new scripts.
Old firmware won't run the new scripts because the new scripts need the micropython.const() function. So please update to the new firmware