Add a unit test for the spawner

[kpaschen]

This adds a test for the case where a pod is unschedulable and never leaves 'pending'.
Also a test for what happens when the pod reflector is added twice, and a basic test about creating a pvc (I only test the easy bit here where it raises an ApiException; for testing non-exception case would need to use a mock or a fixture that ensures the pvc is deleted afterwards).

I made two changes to the spawner that need review from someone who knows this code -- both are in places where a TimeoutException has been caught, and the spawner prints 'restarting pods'. The original code calls 'raise' right after that, and that seemed odd, so I changed it. If you think that's wrong, please let me know!

This brings coverage to 78.19%.

I've also noticed that proxy.py appears unused -- I wasn't sure of the status of that code though.

[betatim]

Looks great. Let's see if someone remembers why/if the raise should be where it was before this PR or if that was a bug.

Otherwise I think merging this is a no brainer :D Thanks for taking the time to increase the coverage by adding some nice tests

[consideRatio]

Suggested change

	c.KubeSpawner.start_timeout = 30 # Do not wait very long.
	c.KubeSpawner.start_timeout = 5 # Do not wait very long.

This duration will increase the time to complete the tests significantly, so I suggest to make this duration quite low.

[yuvipanda]

Well, am here looking at this now :)

I 'solved' the merge conflicts and pushed this up, and will merge this if the tests pass.

[yuvipanda]

Unfortunately it looks like the internals of kubespawner have changed enough in the last 4 years that these tests no longer apply :( I'm going to close this PR for now, with apologies for the delay that caused this - am sorry @kpaschen!