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/qt-creator/package.py

@@ -32,7 +32,7 @@ class QtCreator(Package):
     url      = 'http://download.qt.io/official_releases/qtcreator/4.1/4.1.0/qt-creator-opensource-src-4.1.0.tar.gz'
 
     list_url = 'http://download.qt.io/official_releases/qtcreator/'
-    list_depth = 3
+    list_depth = 2
 
     version('4.1.0',  '657727e4209befa4bf5889dff62d9e0a')