This tests the behaviour when removing three objects referencing each other
in a circle.  This situation cannot be resolved completely, since the removal
events are fired separately.  However, the circle gets "broken up" when
confirming the removal of the first object, and no further confirmation form
are necessary: 

  >>> self.setRoles(('Manager',))
  >>> p = self.portal
  >>> p.doc1.processForm(values={'text':'<a href="doc2">documents...</a>'})
  >>> p.doc2.processForm(values={'text':'<a href="folder1/doc3">linking...</a>'})
  >>> p.folder1.doc3.processForm(values={'text':'<a href="../doc1">in circles.</a>'})
  >>> p.doc1.getReferences()
  [<ATDocument at /plone/doc2>]
  >>> p.doc2.getReferences()
  [<ATDocument at /plone/folder1/doc3>]
  >>> p.folder1.doc3.getReferences()
  [<ATDocument at /plone/doc1>]

We use a browser to try to delete all three documents.  Before we
can do this we need to prevent the test framework from choking on the
exception we intentionally throw (see docs/testRemovalTriggersConfirmation.txt
for more info).  Also, we disable the event count helper (as set in
folder_contents), so that all tests written so far won't need modification:

  >>> self.setStatusCode('LinkIntegrityNotificationException', 200)
  >>> self.disableEventCountHelper()
  >>> browser = self.getBrowser(loggedIn=True)
  >>> browser.open('http://nohost/plone/folder_contents')
  >>> browser.getControl('Test Page 1').selected = True
  >>> browser.getControl('Test Page 2').selected = True
  >>> browser.getControl('Test Folder 1').selected = True
  >>> browser.getControl('Delete').click()
  >>> browser.contents
  '...<a href="http://nohost/plone/doc1"...Test Page 1...
   ...This...Document...is referenced by the following items:...
   ...<li>...<a href="http://nohost/plone/folder1/doc3"...Test Page 3...</li>...
   ...Would you like to delete it anyway?...'

Before we continue with the removal of the item, we test for the presence of
'Test Page 2' in the list of referenced items.  This should not appear as it
links to an object contained in also to be deleted `folder1/`, and this breach
can be filtered out even without the helper:

  >>> '<dt><a href="http://nohost/plone/doc2">Test Page 2</a></dt>' in browser.contents
  False

Now we can continue, i.e. confirm the breaches:

  >>> browser.getControl(name='delete').click()

At this point the remaining integrity breaches can be resolved automatically,
since their target objects are known to be removed as well.  Hence there are
no further confirmation forms:

  >>> browser.url
  'http://nohost/plone/@@folder_contents'
  >>> browser.contents
  '...<dl class="portalMessage...Item(s) deleted...</dl>...'

The documents should have been deleted:

  >>> portal.doc1
  Traceback (most recent call last):
  ...
  AttributeError: doc1
  >>> portal.doc2
  Traceback (most recent call last):
  ...
  AttributeError: doc2
  >>> portal.folder1.doc3
  Traceback (most recent call last):
  ...
  AttributeError: folder1

