[FIX] report.interface: toxml() should return unicode to avoid any encoding issue propagation

It used to return utf-8 data but was brittle in the conversion, and would fail downstream
if the calling code did not pay attention to handle utf-8 data properly.
Returning unicode forces callers to auto-cast to unicode for any string operation, saving
potential trouble later. 
From the addons that currently call toxml(), none use it in a manner that would fail in case
unicode data is returned, so we should be on the safe side there too.

lp bug: https://launchpad.net/bugs/695960 fixed

bzr revid: odo@openerp.com-20110117184444-mxjeneuoa0r5a85n

bin/report/interface.py

@@ -33,16 +33,12 @@ import render
 import urllib
 
 #
-# encode a value to a string in utf8 and converts XML entities
+# coerce any type to a unicode string (to preserve non-ascii characters)
+# and escape XML entities
 #
-def toxml(val):
-    if isinstance(val, str):
-        str_utf8 = val
-    elif isinstance(val, unicode):
-        str_utf8 = val.encode('utf-8')
-    else:
-        str_utf8 = str(val)
-    return str_utf8.replace('&', '&amp;').replace('<','&lt;').replace('>','&gt;')
+def toxml(value):
+    unicode_value = tools.ustr(value)
+    return unicode_value.replace('&', '&amp;').replace('<','&lt;').replace('>','&gt;')
 
 class report_int(netsvc.Service):
     def __init__(self, name, audience='*'):