Fix a crash wish unencodable encoding in the encoder.

JSONEncoder.encode() crashed in Python 3 when encoded bytes keys if the
encoding was not encodable to utf-8 (contained surrogates).

simplejson/_speedups.c

@@ -642,10 +642,13 @@ encoder_stringify_key(PyEncoderObject *s, PyObject *key)
     }
     else if (PyString_Check(key)) {
 #if PY_MAJOR_VERSION >= 3
+        const char *encoding = JSON_ASCII_AS_STRING(s->encoding);
+        if (encoding == NULL)
+            return NULL;
         return PyUnicode_Decode(
             PyString_AS_STRING(key),
             PyString_GET_SIZE(key),
-            JSON_ASCII_AS_STRING(s->encoding),
+            encoding,
             NULL);
 #else /* PY_MAJOR_VERSION >= 3 */
         Py_INCREF(key);
@@ -2599,6 +2602,8 @@ encoder_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     s->encoding = JSON_ParseEncoding(encoding);
     if (s->encoding == NULL)
         goto bail;
+    if (JSON_ASCII_AS_STRING(s->encoding) == NULL)
+        goto bail;
     Py_INCREF(indent);
     s->indent = indent;
     Py_INCREF(key_separator);

simplejson/tests/test_speedups.py

@@ -1,10 +1,12 @@
+from __future__ import with_statement
+
 import sys
 import unittest
 from unittest import TestCase
 
 import simplejson
 from simplejson import encoder, decoder, scanner
-from simplejson.compat import PY3, long_type
+from simplejson.compat import PY3, long_type, b
 
 
 def has_speedups():
@@ -80,3 +82,9 @@ def test_int_as_string_bitcount_overflow(self):
         def test():
             encoder.JSONEncoder(int_as_string_bitcount=long_count).encode(0)
         self.assertRaises((TypeError, OverflowError), test)
+
+    if PY3:
+        @skip_if_speedups_missing
+        def test_bad_encoding(self):
+            with self.assertRaises(UnicodeEncodeError):
+                encoder.JSONEncoder(encoding='\udcff').encode({b('key'): 123})