These built-in functions are exposed as methods in PyPy3.
For scrapy this does not matter as:
1) they do not work for CPython at all
2) get_func_args is checked for presense of an argument in scrapy,
extra "self" does not matter.
But it still makes sense to leave these tests so that we know we
shouldn't use get_func_args for built-in functions/methods.
* 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