Some pycodestyle (PEP8) fixes

Part of #611 (closed)

Before this changes:

3       E741 ambiguous variable name 'l'
5       E305 expected 2 blank lines after class or function definition, found 1
40      W605 invalid escape sequence '\s
75      W504 line break after binary operator

After

40      W605 invalid escape sequence '\s
75      W504 line break after binary operator

Even it was not part of the checks, I have fixed Fix E201, E202, E402 for doc/source/conf.py as well as the fixes were trivial