Localized and user friendly error message

[zhanghai]

[zhanghai]

Needs setlocale(LC_ALL, "");

[zhanghai]

// We only support two locales, the "C" locale (also known as "POSIX"),
// and the "C.UTF-8" locale (also known as "en_US.UTF-8").

https://android.googlesource.com/platform/bionic/+/master/libc/bionic/locale.cpp

[zhanghai]

Maybe we should localize the standard FileSystemException first, plus the "root not available" one.