This patch fixes lyx2lyx running on python 3 for those systems
where the default encoding is not UTF-8, since open by default
uses the default system encoding.
The escaping of symbols read from unicodesymbols was inconsistent, which lead
to wrong replacements (bug 9559). Now the escaping is consistent: unicode_reps
contains unescaped LaTeX commands, the needed escaping for LyX files is
applied in put_cmd_in_ert() and lyx2latex().
Most of the changes are related with dictionaries returning views instead of
lists.
xrange -> range (since xrange is gone in python 3)
The code that is special to support both python 2 and 3 is enclosed in a comment
\# Provide support for both python 2 and 3
and
\# End of code to support for both python 2 and 3
And so later it can be removed safely when python 2 is no longer supported.
