Show traceback, continuing to start kernel if pylab init fails Error message goes directly over stderr (and traceback over stdout), rather than as a pyerr message, which is associated with a particular frontend, and thus ignored because startup actions were not requested by anyone. This better matches the terminal behavior, where `ipython --pylab` without matplotlib installed shows a traceback, but continues to start. In the qtconsole the traceback will come in below the banner, but in the notebook the message will not arrive until after the first execution. closes gh-990, closes gh-991.