Update the URL to the exceptions documentation on RTD
GH-71 get the portal path with absolute_url_path so that it content.get works with sites which don't have the portal in the zope root

I don't know a nice way to write a test for this since the test layer assumes that the portal is in the site root. I have tested it manually with a local instance.
Remove unused variable
Merge pull request #78 from cillianderoiste/GH-71

#GH-71 fix content.get path to also work when the portal is not in the zope root