explicitly mark unused variables found by pylint with _ or dummy

pylint don't ignores unused variables with '_' in the name, even when
they are started with '_'. This bug is already fixed upstream, to fix
this in all versions of pylint custom dummy-variables-rgx is used
'_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy'

{
    "url":"ws://127.0.0.1:8888",
    "realm":"Automation",
    "ID":"wamptest",
    "password":"1234567890",
    "key":"ABCDEFGHIJ"
}