stricter linting – follow up #413

[jGaboardi]

• Stricter linting – follow up Maint work for update supported Python versions, CI environments, et.c #413
• This touches more lines of code than I thought it would... As usual, I can split if desired.

[codecov]

Codecov Report

Merging #418 (a621733) into main (bf7134a) will decrease coverage by 0.0%.
The diff coverage is 98.6%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #418     +/-   ##
=======================================
- Coverage   77.7%   77.7%   -0.0%     
=======================================
  Files         27      27             
  Lines       2636    2634      -2     
=======================================
- Hits        2048    2046      -2     
  Misses       588     588             

Files	Coverage Δ
spopt/BaseClass.py	73.3% <ø> (ø)
spopt/locate/base.py	94.3% <100.0%> (ø)
spopt/locate/coverage.py	97.8% <ø> (ø)
spopt/locate/p_center.py	100.0% <ø> (ø)
spopt/locate/p_dispersion.py	100.0% <ø> (ø)
spopt/locate/p_median.py	97.2% <ø> (-<0.1%)	⬇️
spopt/locate/util.py	100.0% <ø> (ø)
spopt/region/azp.py	35.8% <100.0%> (ø)
spopt/region/azp_util.py	36.3% <ø> (ø)
spopt/region/base.py	97.6% <100.0%> (ø)
... and 9 more