Make the should_trace_cache test a little more bullet-proof.
Make the should_trace_cache test a little more bullet-proof.

jayhetee/coveragepy,blueyed/coveragepy,larsbutler/coveragepy,larsbutler/coveragepy,hugovk/coveragepy,nedbat/coveragepy,hugovk/coveragepy,jayhetee/coveragepy,7WebPages/coveragepy,nedbat/coveragepy,hugovk/coveragepy,larsbutler/coveragepy,nedbat/coveragepy,larsbutler/coveragepy,7WebPages/coveragepy,7WebPages/coveragepy,hugovk/coveragepy,nedbat/coveragepy,larsbutler/coveragepy,7WebPages/coveragepy,nedbat/coveragepy,blueyed/coveragepy,blueyed/coveragepy,hugovk/coveragepy,jayhetee/coveragepy,blueyed/coveragepy,jayhetee/coveragepy,blueyed/coveragepy,jayhetee/coveragepy