pyfftw tests are not being run

I just noticed that continuous integration does not run pyfftw tests, even when the package should be available. This accounts for the 2400 tests that are currently skipped in the pipelines. I'm not sure why this happens. The relevant tests in test_fft_operator.py are guarded by

        if module == "fftw" and "pyfftw" not in di:
            raise SkipTest

which looks correct to me.