Catch KeyboardInterrupt during test run...

...so that one can ^C a test run and still get a report of failed tests
and stack traces.
Instruct coverage instance to cover requested packages only.
Merge pull request #739 from chebee7i/cover_package

Instruct coverage instance to cover requested packages only.
Merge pull request #682 from kevinjqiu/ignore-keyboard-interrupt

Catch KeyboardInterrupt during test run.
Fix #690: Don't traceback when coverage reports fail.

Under Jython this step fails badly and tanks Nose.  Instead, emit a
warning about the failure to create the coverage reports, and move on.