The following PR replaces the sequence of statement

    d = d1.copy()
    d.update(d2)

(where d1 and d2 are dicts) with a form proposed in PEP 448:

    d = {**d1, **d2}

or equivalent.

Besides functools, where using the new syntax makes the code clearer, there are not much occurrences of such idiom: only in yet 5 files, 1-2 times per file.