Use UTF-8 instead of Latin-1

This decoding happens when a non-unicode string is rendered in
a DTML template.

The decoding happens in 'join_unicode' which takes no arguments. But a
better fix for this would perhaps be to make that function take an encoding
argument (or boolean keyword argument to enable UTF-8).

However, backwards compatibility here seems rather pointless.

CHANGES.txt

@@ -4,6 +4,7 @@ Changelog
 2.13.5 (unreleased)
 -------------------
 
+- Use 'utf-8' to decode non-unicode strings instead of 'latin-1'.
 
 2.13.4 (2017-02-15)
 -------------------

src/DocumentTemplate/cDocumentTemplate.c

@@ -925,7 +925,7 @@ _join_unicode(PyObject *prejoin)
             PyObject *item = PyList_GetItem(list,i);
             if(PyString_Check(item))
             {
-                PyObject *unicode = PyUnicode_DecodeLatin1(PyString_AsString(item),PyString_Size(item),NULL);
+                PyObject *unicode = PyUnicode_DecodeUTF8(PyString_AsString(item),PyString_Size(item),NULL);
                 if(unicode)
                 {
                     PyList_SetItem(list,i,unicode);

src/DocumentTemplate/tests/testDTMLUnicode.py

@@ -55,25 +55,25 @@ def testAB(self):
     def testUB(self):
         html=self.doc_class('<dtml-var a><dtml-var b>')
         expected = u'hello\xc8'
-        res = html(a=u'hello',b=chr(200))
+        res = html(a=u'hello',b='\xc3\x88')
         assert res == expected, `res`
 
     def testUB2(self):
         html=self.doc_class('<dtml-var a><dtml-var b>')
         expected = u'\u07d0\xc8'
-        res = html(a=unichr(2000),b=chr(200))
+        res = html(a=unichr(2000),b='\xc3\x88')
         assert res == expected, `res`
 
     def testUnicodeStr(self):
         html=self.doc_class('<dtml-var a><dtml-var b>')
         expected = u'\u07d0\xc8'
-        res = html(a=force_str(unichr(2000)),b=chr(200))
+        res = html(a=force_str(unichr(2000)),b='\xc3\x88')
         assert res == expected, `res`
 
     def testUqB(self):
         html=self.doc_class('<dtml-var a html_quote><dtml-var b>')
         expected = u'he&gt;llo\xc8'
-        res = html(a=u'he>llo',b=chr(200))
+        res = html(a=u'he>llo',b='\xc3\x88')
         assert res == expected, `res`
 
     def testSize(self):