Port to Python 3

[rhl-bthr]

No description provided.

[quozl]

Reviewed to 4fc05b3.

[rhl-bthr]

Although this PR is complete and (probably) won't need updating, I have left it as in-porgress since the six port of Sugar-Toolkit-GTK+ 3 is not yet complete and gets tested as I port activities.

@quozl @walterbender Is this approach fine or can there be a better alternate to this

[quozl]

Without the toolkit ported, Write would stop working if we merged this. We'll need to go through a toolkit release cycle first. sugarlabs/sugar-toolkit-gtk3#382 updated "release new version".

[rhl-bthr]

Sorry, rephrasing my question,
Should I keep opening such In-progress PRs (not to be merged) of porting activities to Python 3, since it helps in testing my six port of Sugar-Toolkit-GTK3

[quozl]

Create a branch python3 in the activity, and make the pull request against that branch?

[rhl-bthr]

Sure, will do the same in future, Thank you

[quozl]

Rebased against new master and pushed with --force.

[rhl-bthr]

This and other PRs for porting activities to Python 3 are open.
I've left the ones running successfully with sugar-toolkit-gtk3/python3-port, as open.

[quozl]

Thanks.

[quozl]

Rebased against new master and pushed with --force to the python3 branch because the repository associated with this pull request has vanished. I've no idea how to push to the pull request once that happens.