tests: rename _bytespath() to _sys2bytes() and _strpath() to _sys2str() The names were not general enough because e.g. _strpath() was used for converting IP addresses.

tests: avoid implicit conversion of str to unicode On Python 2, str.encode('ascii') implicitly converts the string to unicode and then back to str. Since the converted value is a path, _bytespath can be used instead.

tests: avoid implicit conversion of str to unicode On Python 2, str.encode('ascii') implicitly converts the string to unicode and then back to str. Since the point of this expression is to convert a bool to a str, the '%r' conversion specifier can be used instead in the format string.