Expand ~ before quoting notebook_dir

[parente]

closes #878

[parente]

Don't merge quite yet. Testing a bit.

[parente]

Nope. Expands too early for sudospawner.

[parente]

Restoring the original, unquoted --notebook_dir=%s template in spawner.py fixes the ~ expansion bug. It's questionable whether this is trading one fix for other problems, however.

[minrk]

I think this is a bug for the single-user server to fix (by calling expanduser), and not to change here. The reason to not change it here is that the quotes were added to deal with an issue in traitlets CLI parsing, to ensure the result is a string (i.e. adding quotes shouldn't change the value).

I also don't think the shell expansion will work for Spawners that launch without instantiating a shell (shell=True for Popen), because raw command-launching doesn't expand ~ (I think).

[willingc]

Thanks @parente and @minrk :D