fix: save_png doesn't work when character \xa0 is used

[mariobuikhuizen]

The character \xa0 is converted to   when .outerHTML() is called, causing an error in the data-URL where the outer HTML is used.

Code changes

Revert &nbps;, generated by .outerHtml(), back to the original character \xa0.

User-facing changes

save_png() will now work when \xa0 is used.

Steps to reproduce

Run the following:

from bqplot import *

x_sc = LinearScale()
y_sc = LinearScale()

scatter_chart = Scatter(x=x_data, y=y_data, scales={'x': x_sc, 'y': y_sc})

x_ax = Axis(label='X', scale=x_sc)
y_ax = Axis(label='Y', scale=y_sc, orientation='vertical')

fig = Figure(title="Ti \xa0 tle", marks=[scatter_chart], axes=[x_ax, y_ax])
fig

fig.save_png("fig.png")

Notice the save dialog is not appearing.

The dataURL produced with  :

[mariobuikhuizen]

Some other unicode characters are converted to entites, like \u2003 ->   and
\u2009 ->  , but they just work.

[maartenbreddels]

We looked into this a bit, but documentation is scarce on this, and this is at least an improvement. Thanks @mariobuikhuizen

[maartenbreddels]

meeseeksdev please backport to 0.12.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 0.12.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 4d5c2932d8d55e1af96e7129f0550c18c0c3b977

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am "Backport PR #1644: fix: save_png doesn't work when character \\xa0 is used"

4. Push to a named branch:

git push YOURFORK 0.12.x:auto-backport-of-pr-1644-on-0.12.x

5. Create a PR against branch 0.12.x, I would have named this PR:

"Backport PR #1644 on branch 0.12.x (fix: save_png doesn't work when character \xa0 is used)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.