also str representation of unicode character is different.

page templates unicode resolver already takes care of coercing when
needed and this is directly compatible with python2 and python3
Co-authored-by: Kazuhiko SHIOZAKI <kazuhiko@nexedi.com>

This only works on python2

for same reason as the xhtml_style version, there is no problem with
having more than one listbox, see d2dedca3 (core: remove useless log
in Base_callDialogMethod, 2020-07-03)

this is not used and cause a SyntaxWarning

This was based on libraries that were never ported to python3. If this
is still needed, it would have to be reimplemented with other newer
technologies.

See merge request nexedi/erp5!1932

Use same label as the action, "Preview"