Odd message while building Python from tip

[Chris Angelico]

I don't think I've ever seen this message before. This is just after
'hg pull -u' to get to the latest CPython (my previous build was about
a month ago). 'make' succeeded, but concluded with this message:

running build_ext
The following modules found by detect_modules() in setup.py, have been
built by the Makefile instead, as configured by the Setup files:
atexit                pwd                   time

And then proceeded to run build_scripts as normal.

It doesn't look like an error, and those three modules can happily be
imported by "./python" and by the freshly-installed "python3.7". It's
curious though. Any explanation?

ChrisA