How to use PCP with a version of Python other than 3.6?

Issue

• After alternatives --set python3 /usr/bin/python3.8, pcp or dstat caused errors.

  $ sudo alternatives --set python3 /usr/bin/python3.8
  $ dstat
  Traceback (most recent call last):
  File "/usr/bin/dstat", line 30, in <module>
    from pcp import pmapi, pmconfig
  ModuleNotFoundError: No module named 'pcp'
  $ pcp iostat
  Traceback (most recent call last):
  File "/usr/libexec/pcp/bin/pcp-iostat", line 21, in <module>
    from pcp import pmapi, pmcc
  ModuleNotFoundError: No module named 'pcp'