'Adds more filters to the existing list of error-message filters.'

def AddFilters(self, filters):

    for filt in filters.split(','):
        clean_filt = filt.strip()
        if clean_filt:
            self.filters.append(clean_filt)
    for filt in self.filters:
        if (not (filt.startswith('+') or filt.startswith('-'))):
            raise ValueError(('Every    filter    in    --filters    must    start    with    +    or    -    (%s    does    not)' % filt))
