def next(self):
if self.current_token == len(self.tokens):<EOL><INDENT>return None<EOL><DEDENT>token = self.tokens[self.current_token]<EOL>if token["<STR_LIT:type>"] == "<STR_LIT>":<EOL><INDENT>self.line += <NUM_LIT:1><EOL>self.line_start = token["<STR_LIT:start>"]<EOL><DEDENT>self.current_token += <NUM_LIT:1><EOL>if token["<STR_LIT:type>"] == "<STR_LIT>":<EOL><INDENT>self.error("<STR_LIT>")<EOL><DEDENT>return token<EOL>
Return the next token.  Keep track of our current position in the
config for nice errors.