> The documentation issue was fixed in issue23738. The documentation no longer claims that ns can be None. If specified it must be a tuple of floats.

tuple of integers, not tuple a floats.

Python 3.9 documentation says: "If ns is specified, it must be a 2-tuple of the form (atime_ns, mtime_ns) where each member is an int expressing nanoseconds." which is correct.

Python 3.9 now emits a DeprecationWarning when passing floats:

vstinner@apu$ ./python
Python 3.9.0a0 (heads/pr/15701-dirty:a0f335c74c, Sep  6 2019, 17:38:14) 
>>> import os
>>> os.utime("x", ns=(1, 1))
>>> os.utime("x", ns=(0.1, 1))
<stdin>:1: DeprecationWarning: an integer is required (got type float).  Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.