title: Nose test runner finding all tests except a tag
body: <p>I'm trying to figure out if there's a way to have the nose test runner run all tests except for those with a specific tag. Looks like this is possible with attributes but I don't see if there's a way to do it with tags, which are a subset of attributes.</p>
  
  <p>Currently I use tags by calling</p>
  
  <pre><code>nosetests -a tags='tag'
  </code></pre>
  
  <p>my tagged tests look like:</p>
  
  <pre><code>@attr(tags=['foo', 'bar', 'baz'])
      def test_some_stuff(self):
  </code></pre>
  
  <p>But if I want to run all test except 'baz' tagged, how would I do that?</p>
  
  <p>I've tried expressions like</p>
  
  <pre><code>nosetests -A 'not baz'
  nosetests -a '!baz'
  nosetests tags='!baz'
  </code></pre>
  
  <p>But those don't seem to have any effect on anything but attributes. And I don't see an example of excluding tags in the docs: <a href="http://nose.readthedocs.org/en/latest/plugins/attrib.html" rel="nofollow">http://nose.readthedocs.org/en/latest/plugins/attrib.html</a></p>
  
  <p>I'd rather not have to add a new tag just for exclusion to this large test suite I'm working with and have to remember to always add a fake 'exclusion tag'.</p>