Fix TypeErrors

[jchnkl]

• Use bytes-like objects instead of str
• basestring does not exist in python 3

[wolfhechel]

Thanks for your PR. I've mostly abandoned this code since I haven't been suing wpactrl for quite some time, so it's much appreciated that you're contributing with some P3 compatibility.

However, you've changed the return of the wpa_ctrl_attach_helper to return False if socket return is not "OK". This breaks with for instance socket timeouts which returns -2 from wpa_ctrl_request. I'd appreciate if you could change it back to return ret, then I'd gladly accept it.