Coding style: fix pep8 + flake8 issues

Coding style: fix pep8 + flake8 issues

Fix:

| W605 invalid escape sequence '\s'

by using re.compile(r'...') instead of re.compile("...")

Fix:

| E261 at least two spaces before inline comment

introduced in commit ed5b633be961ef6b3

Fix flake8 issues:

| grml2usb:409:5: F841 local variable 'e' is assigned to but never used
| grml2usb:557:34: W504 line break after binary operator
| grml2usb:559:34: W504 line break after binary operator
| grml2usb:737:37: W504 line break after binary operator
| grml2usb:1615:13: F841 local variable 'error' is assigned to but never used
| grml2usb:1641:9: F841 local variable 'error' is assigned to but never used
| grml2usb:1665:5: F841 local variable 'error' is assigned to but never used
| grml2usb:1826:30: W504 line break after binary operator
| grml2usb:1832:30: W504 line break after binary operator

The https://www.flake8rules.com/rules/W503.html vs
https://www.flake8rules.com/rules/W504.html is strange,
though let's use what black(1) (see https://github.com/psf/black)
uses.