'unicode' is not available in python3, so remove the use of it. And for
python3 'bytes' string might need to be converted to a regular string

Signed-off-by: Qin Zhang （张琴） <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>

Note by Bernhard: As per the agreement with Andrew in xapi-project#18, we shall
keep master py2-compatible and py3-only changes go to a py3 branch:

Andrew wrote:
> However, master needs to remain atomically py2 or py3 compatible,
> and not a mix of fixes which leaves it broken in both. [...]
> please keep all commits which break compatibility with py2 in a
> separate single PR so it can be merged all in one go.
> The final commit on the py3 branch should [...]
Reference:
xapi-project#18 (comment)

Therefore, I'll squash this commit with the next commit for fixing
it up keep master py2-compatible, at least until all py3 checks and
a complete manual test was done by QA.

Original commit message by Qin Zhang （张琴）:
Remove the use of 'encode' as it's used to turn a Unicode string into a regular string in Python2

Final Remarks by Bernhard, for completeleness:
- This commit also adds conversion from curses input bytes to str.
- Rebased to apply on the current master branch.

Co-authored-by: Bernhard Kaindl <[email protected]>
Signed-off-by: Qin Zhang （张琴） <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>

Signed-off-by: Bernhard Kaindl <[email protected]>