* run test_utils_python in Python 3;
* make tests for 'errors' argument more explicit
* add missing test_ prefix utf_16_strings_contain_null_bytes;
* cleanup test names.
* stringify_dict is deprecated
* is_writable is deprecated
* setattr_default is deprecated
* get_spec is untested
* re_rsearch is untested
* retry_on_eintr is untested