Add error matching dispatch for exception type
* usage:  with error.expected(KeyError):   x = d['nonexistentkey']
Prevent tests hang when ip_echo is down.

It was here before, but when I was changing the fixture the last time, I introduced this back. py.test touches everything to find a fixture, so it was touching the lazycached host
Merge pull request #736 from mfalesni/prevent_touching_error

Prevent tests hang when ip_echo is down.
Fix slowdown in collection

InfoBlock elements were generally defined in modules and as modules were
loaded at collection time, the collapsing of any InfoBlock elements
invoked an ssh and db check for the version. The .locate() is now
deferred to when the _box_locator is actually used within the code.
Merge pull request #737 from psav/fix_collection

Fix slowdown in collection