pylint #20385 style checking ideas: ASCII-only, weird parentheses, whitespace [open]

Here a some situations or regex that should not appear in some projects:

• del(a) # not a function
• except (Exc) # not a function
• r'[x80-xff]' # non-ASCII character literal
• r'([([]sS)|(Ss[)]])' # gratuitous whitespace in () or []