skipping one unittest assertion?

[Roy Smith]

Is there any way to skip a single assertion in a unittest test method?  
I know I can @skip or @expectedFailure the method, but I'm looking for 
something finer-grain than that.

There's one particular assertion in a test method which depends on 
production code that hasn't been written yet.  I could factor that out 
into its own test methods and @skip that, but it would be cleaner to be 
able to mark the particular assertion.

(using python 2.6, but importing unittest2 from 2.7)