pyramid exception handling workflow

workflow.txt

   pyramid_retry   +-------->    if exc not retryable, render response
                                 if exc retryable, ignore exc and try again
        +
        |
        |
        v

pyramid_debugtoolbar

        +
        |
        |
        v

    pyramid_tm     +-------->    if exc caught then abort and reraise
                                 if request.exception then abort and return response
        +                        if abort or commit raises, render response
        |
        |
        v

     excview       +-------->    if exc caught, render response and set request.exception
                                                if no exception then reraise
        +
        |
        |
        v

       app