Issue in release script mass_comment.py

Error: requests.exceptions.InvalidURL: Failed to parse: [https://api.github.com/graphql](https://api.github.com/graphql)

I opened that link and it says:

{"message":"API rate limit exceeded for 104.133.8.67. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)","documentation_url":"https://developer.github.com/v3/#rate-limiting"}

Another minor issue: when I was prompted to enter my GitHub access token, I have to enclose it in double quote, otherwise I will run into:

SyntaxError: unexpected EOF while parsing

Imported from Jira [BEAM-10966](https://issues.apache.org/jira/browse/BEAM-10966). Original Jira may contain additional context.
Reported by: robinyqiu.