Process data block for OUTPUT token.

def process_output(self, data, output_prompt,
                       input_lines, output, is_doctest, image_file):
        """Process data block for OUTPUT token."""
        if is_doctest:
            submitted = data.strip()
            found = output
            if found is not None:
                found = found.strip()

                # XXX - fperez: in 0.11, 'output' never comes with the prompt
                # in it, just the actual output text.  So I think all this code
                # can be nuked...

                # the above comment does not appear to be accurate... (minrk)

                ind = found.find(output_prompt)
                if ind<0:
                    e='output prompt="%s" does not match out line=%s' % \
                       (output_prompt, found)
                    raise RuntimeError(e)
                found = found[len(output_prompt):].strip()

                if found!=submitted:
                    e = ('doctest failure for input_lines="%s" with '
                         'found_output="%s" and submitted output="%s"' %
                         (input_lines, found, submitted) )
                    raise RuntimeError(e)