def _verify(self, payload):
if not payload:  <EOL><INDENT>raise ze.ParamNotPassed<EOL><DEDENT>for templt in payload:<EOL><INDENT>if os.path.isfile(str(self.basedir.joinpath(templt["<STR_LIT:filename>"]))):<EOL><INDENT>try:<EOL><INDENT>with open(str(self.basedir.joinpath(templt["<STR_LIT:filename>"]))):<EOL><INDENT>pass<EOL><DEDENT><DEDENT>except IOError:<EOL><INDENT>raise ze.FileDoesNotExist(<EOL>"<STR_LIT>"<EOL>% str(self.basedir.joinpath(templt["<STR_LIT:filename>"]))<EOL>)<EOL><DEDENT><DEDENT>else:<EOL><INDENT>raise ze.FileDoesNotExist(<EOL>"<STR_LIT>"<EOL>% str(self.basedir.joinpath(templt["<STR_LIT:filename>"]))<EOL>)<EOL><DEDENT><DEDENT>
ensure that all files to be attached exist
open()'s better than exists(), cos it avoids a race condition