[FIX] scaffold: correctly decode utf8 templates

As its documentation notes[0], Jinja2 only processes unicode template
data (or pure ASCII, which will implicitly decode to unicode).

The scaffolding system would read raw scaffolding data in memory (both
templates and passthrough non-templates), but fail to decode templates
before handing them to Jinja, blowing rendering up if templates
contained non-ascii.

Fix #11331 by always decoding templates from UTF8 before handing them
to jinja. This is backwards-compatible, ascii templates work as they
used to, non-ascii UTF8 templates now work correctly, non-ascii
non-UTF8 templates what are you doing?

[0] http://jinja.pocoo.org/docs/dev/api/#unicode

openerp/cli/scaffold.py

@@ -126,7 +126,7 @@ class template(object):
                 if ext not in ('.py', '.xml', '.csv', '.js', '.rst', '.html', '.template'):
                     f.write(content)
                 else:
-                    env.from_string(content)\
+                    env.from_string(content.decode('utf-8'))\
                        .stream(params or {})\
                        .dump(f, encoding='utf-8')