py-psutil: updated to 5.9.1

5.9.1
=====

**Enhancements**

- 1053_: dropped support for Python 2.6.  (patches by Matthieu Darbois and Hugo van Kemenade)
- 2050_, [Linux]: increase ``read(2)`` buffer size from 1k to 32k when reading
  ``/proc`` pseudo files line by line. This should help having more consistent
  results.
- 2057_, [OpenBSD]: add support for `cpu_freq()`_.
- 2107_ [Linux]: `Process.memory_full_info()`_ (reporting process USS/PSS/Swap
  memory) now reads ``/proc/pid/smaps_rollup`` instead of ``/proc/pids/smaps``,
  which makes it 5 times faster.

**Bug fixes**

- 2048_: ``AttributeError`` is raised if ``psutil.Error`` class is raised
  manually and passed through ``str``.
- 2049_, [Linux]: `cpu_freq()`_ erroneously returns ``curr`` value in GHz while
  ``min`` and ``max`` are in MHz.
- 2050_, [Linux]: `virtual_memory()`_ may raise ``ValueError`` if running in a
  LCX container.

(adam)