On Windows, don't encode filenames in the import machinery

Python/future.c

 #include "Python.h"
 #include "Python-ast.h"
 #include "node.h"
 #include "token.h"
 #include "graminit.h"
 #include "code.h"
 #include "symtable.h"
 
 #define UNDEFINED_FUTURE_FEATURE "future feature %.100s is not defined"
 #define ERR_LATE_FUTURE \
 "from __future__ imports must occur at the beginning of the file"
 
 static int
-future_check_features(PyFutureFeatures *ff, stmt_ty s, const char *filename)
+future_check_features(PyFutureFeatures *ff, stmt_ty s, PyObject *filename)
 {
     int i;
     asdl_seq *names;
 
     assert(s->kind == ImportFrom_kind);
 
     names = s->v.ImportFrom.names;
     for (i = 0; i < asdl_seq_LEN(names); i++) {
         alias_ty name = (alias_ty)asdl_seq_GET(names, i);
         const char *feature = _PyUnicode_AsString(name->name);
@@ skipping 11 matching lines @@
             continue;
         } else if (strcmp(feature, FUTURE_PRINT_FUNCTION) == 0) {
             continue;
         } else if (strcmp(feature, FUTURE_UNICODE_LITERALS) == 0) {
             continue;
         } else if (strcmp(feature, FUTURE_BARRY_AS_BDFL) == 0) {
             ff->ff_features |= CO_FUTURE_BARRY_AS_BDFL;
         } else if (strcmp(feature, "braces") == 0) {
             PyErr_SetString(PyExc_SyntaxError,
                             "not a chance");
-            PyErr_SyntaxLocationEx(filename, s->lineno, s->col_offset);
+            PyErr_SyntaxLocationObject(filename, s->lineno, s->col_offset);
             return 0;
         } else {
             PyErr_Format(PyExc_SyntaxError,
                          UNDEFINED_FUTURE_FEATURE, feature);
-            PyErr_SyntaxLocationEx(filename, s->lineno, s->col_offset);
+            PyErr_SyntaxLocationObject(filename, s->lineno, s->col_offset);
             return 0;
         }
     }
     return 1;
 }
 
 static int
-future_parse(PyFutureFeatures *ff, mod_ty mod, const char *filename)
+future_parse(PyFutureFeatures *ff, mod_ty mod, PyObject *filename)
 {
     int i, done = 0, prev_line = 0;
     stmt_ty first;
 
     if (!(mod->kind == Module_kind || mod->kind == Interactive_kind))
         return 1;
 
     if (asdl_seq_LEN(mod->v.Module.body) == 0)
         return 1;
 
@@ skipping 24 matching lines @@
            statement and a doc string.
         */
 
         if (s->kind == ImportFrom_kind) {
             identifier modname = s->v.ImportFrom.module;
             if (modname &&
                 !PyUnicode_CompareWithASCIIString(modname, "__future__")) {
                 if (done) {
                     PyErr_SetString(PyExc_SyntaxError,
                                     ERR_LATE_FUTURE);
-                    PyErr_SyntaxLocationEx(filename, s->lineno, s->col_offset);
+                    PyErr_SyntaxLocationObject(filename, s->lineno, s->col_offset);
                     return 0;
                 }
                 if (!future_check_features(ff, s, filename))
                     return 0;
                 ff->ff_lineno = s->lineno;
             }
             else {
                 done = 1;
             }
         }
         else {
             done = 1;
         }
     }
     return 1;
 }
 
 
 PyFutureFeatures *
-PyFuture_FromAST(mod_ty mod, const char *filename)
+PyFuture_FromASTObject(mod_ty mod, PyObject *filename)
 {
     PyFutureFeatures *ff;
 
     ff = (PyFutureFeatures *)PyObject_Malloc(sizeof(PyFutureFeatures));
     if (ff == NULL) {
         PyErr_NoMemory();
         return NULL;
     }
     ff->ff_features = 0;
     ff->ff_lineno = -1;
 
     if (!future_parse(ff, mod, filename)) {
         PyObject_Free(ff);
         return NULL;
     }
     return ff;
 }
+
+
+PyFutureFeatures *
+PyFuture_FromAST(mod_ty mod, const char *filename_str)
+{
+    PyFutureFeatures *ff;
+    PyObject *filename;
+
+    filename = PyUnicode_DecodeFSDefault(filename_str);
+    if (filename == NULL)
+        return NULL;
+    ff = PyFuture_FromASTObject(mod, filename);
+    Py_DECREF(filename);
+    return ff;
+}