'Find all source files in the source dir and put them in self.found_docs.'

def find_files(self, config):

    exclude_dirs = [d.replace(SEP, path.sep) for d in config.exclude_dirs]
    exclude_trees = [d.replace(SEP, path.sep) for d in config.exclude_trees]
    self.found_docs = set(get_matching_docs(self.srcdir, config.source_suffix, exclude_docs=set(config.unused_docs), exclude_dirs=exclude_dirs, exclude_trees=exclude_trees, exclude_dirnames=(['_sources'] + config.exclude_dirnames)))
