Fix 404 after jupyterhub 1.0.0

[kinow]

Finally found a way to fix this one. Tested locally.

It worked before when the button was pointing to /user/$USER/ with the trailing slash. Now it copies the behaviour of jupyterhub's AddSlashHandler.

[kinow]

And later if we keep using JupyterHub as a dependency in the ui server (there is work-in-progress that may eliminate that dependency by @MartinRyan), we can remove our implementation and simply import theirs.

[codecov-io]

Codecov Report

Merging #39 into master will decrease coverage by 0.78%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##           master      #39      +/-   ##
==========================================
- Coverage   68.13%   67.34%   -0.79%     
==========================================
  Files           2        2              
  Lines          91       98       +7     
  Branches        6        6              
==========================================
+ Hits           62       66       +4     
- Misses         29       32       +3

Impacted Files	Coverage Δ
cylc_singleuser.py	67.5% <100%> (ø)	⬆️
handlers.py	67.24% <72.72%> (-1.39%)	⬇️

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[dwsutherland]

LGTM

[sadielbartholomew]

Sorry @kinow, I am too late to the game on this one as I see it has already been merged, buy FYI & for future, there is a useful Tornado decorator, @tornado.web.addslash, which will automatically add in a / to the URL if not present.

(I discovered it & used it in my recent work for a Rose service (PR metomi/rose#2288 if you are interested, see https://github.com/metomi/rose/blob/2dd607f6ca8ed251c2559265a9e58a7fed2fe9f0/lib/python/rosie/ws.py#L166-L168.)

This is a neat custom solution for the problem though!

[kinow]

I think that worked @sadielbartholomew ! Much simpler, thanks!