Issue #8965: initfsencoding() doesn't change the encoding on Mac OS X

File system encoding have to be hardcoded to "utf-8" on Mac OS X. r81190
introduced a regression: the encoding was changed depending on the locale.

Python/pythonrun.c

@@ -703,6 +703,7 @@ initfsencoding(void)
 #if defined(HAVE_LANGINFO_H) && defined(CODESET)
     char *codeset;
 
+    if (Py_FileSystemDefaultEncoding == NULL) {
         /* On Unix, set the file system encoding according to the
            user's preference, if the CODESET names a well-known
            Python codec, and Py_FileSystemDefaultEncoding isn't
@@ -721,6 +722,7 @@ initfsencoding(void)
                 "fallback to utf-8\n");
         Py_FileSystemDefaultEncoding = "utf-8";
         Py_HasFileSystemDefaultEncoding = 1;
+    }
 #endif
 
     /* the encoding is mbcs, utf-8 or ascii */