Add better tests for web.py; fix some bugs found with spidering.

- _spider in web.py was actually failing to spider deeper than a certain
  point.
- Fixed multiprocessing pools to not use daemons and to allow recursive
  spawning.
- Added detailed tests for spidering and for finding archive versions.
- left some xfail URL finding exercises for the reader.
- Fix noqa annotations for some @when decorators

var/spack/repos/builtin/packages/py-scikit-learn/package.py

@@ -30,8 +30,6 @@ class PyScikitLearn(PythonPackage):
 
     homepage = "https://pypi.python.org/pypi/scikit-learn"
     url      = "https://pypi.io/packages/source/s/scikit-learn/scikit-learn-0.18.1.tar.gz"
-    list_url = "https://pypi.python.org/pypi/scikit-learn"
-    list_depth = 2
 
     version('0.18.1', '6b0ff1eaa5010043895dd63d1e3c60c9')
     version('0.15.2', 'd9822ad0238e17b382a3c756ea94fe0d')