def _append_base_arguments(self):
if self.exc and self.only:<EOL><INDENT>raise PackerException('<STR_LIT>')<EOL><DEDENT>elif self.exc:<EOL><INDENT>self._add_opt('<STR_LIT>'.format(self._join_comma(self.exc)))<EOL><DEDENT>elif self.only:<EOL><INDENT>self._add_opt('<STR_LIT>'.format(self._join_comma(self.only)))<EOL><DEDENT>for var, value in self.vars.items():<EOL><INDENT>self._add_opt("<STR_LIT>")<EOL>self._add_opt("<STR_LIT>".format(var, value))<EOL><DEDENT>if self.var_file:<EOL><INDENT>self._add_opt('<STR_LIT>'.format(self.var_file))<EOL><DEDENT>
Appends base arguments to packer commands.

        -except, -only, -var and -var-file are appeneded to almost
        all subcommands in packer. As such this can be called to add
        these flags to the subcommand.