pyperformance: psutil is never installed on Windows

On Windows, it turns out pyperf (and hence pyperformance) will always print a warning when psutil is not installed. The warning is:

WARNING: unable to increase process priority

It is printed by _process_priority(). (Note the if not MS_WINDOWS: return right before.)

The function set_priority() silently returns None, but the caller prints the warning in that case.

So now for every benchmark run by pyperformance it calls this _process_priority() function for each run, printing the warning each time (maybe 10 times per run).

The solution of course is to install psutil. But no matter what I do, because the way venvs used to run the benchmark are created, those venvs do not get psutil installed, even if it is installed in site-packages. (At least, when running from a dev environment.)

• I tried adding "psutil" to the install_requires line in pyperformance’s setup.py, but that doesn’t seem to help.
• psutil is already listed in requirements.in, so that doesn’t seem to make a difference.
• It is also listed in pyperformance/data-files/requirements.txt, apparently with no effect.

So how do I add this dependency to every package? Surely there’s a more elegant way than adding it to every benchmark-specific requirements.txt file in pyperformance/data-files/benchmarks?