Adopt PEP-8 for whitespace recommendations

[ischoegl]

Changes proposed in this pull request

The current style guide for whitespace (per CONTRIBUTING.md) recommends:

• Use whitespaces to improve code readability (examples: after commas; before and
  after mathematical operators (+/-/*// except ^), binary operators
  (&&/||/...), and comparisons (</>/==/...); before and after equality

does not follow PEP-8 recommendations. This PR updates Cantera style guide recommendations to become consistent.

In addition:

• Update Python documentation instructions
• Fix typo in SConstruct

If applicable, fill in the issue number this pull request is fixing

Closes Cantera/enhancements#184

If applicable, provide an example illustrating new features this pull request is introducing

Per PEP-8:

# Correct:
i = i + 1
submitted += 1
x = x*2 - 1
hypot2 = x*x + y*y
c = (a+b) * (a-b)

and

# Wrong:
i=i+1
submitted +=1
x = x * 2 - 1  # <-- current Cantera style 
hypot2 = x * x + y * y  # <-- current Cantera style 
c = (a + b) * (a - b)  # <-- current Cantera style 

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review

[codecov]

Codecov Report

Merging #1584 (590ac73) into main (4b30fa7) will decrease coverage by 0.01%.
Report is 4 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1584      +/-   ##
==========================================
- Coverage   70.51%   70.51%   -0.01%     
==========================================
  Files         379      379              
  Lines       59118    59117       -1     
  Branches    21237    21237              
==========================================
- Hits        41686    41685       -1     
  Misses      14359    14359              
  Partials     3073     3073              

see 1 file with indirect coverage changes

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[speth]

Thanks, @ischoegl. Just a couple of comments for your consideration.

[ischoegl]

Thanks, @speth. I believe this is ready to merge.