Automatically retry requests that fail with 429 Too Many Requests

[rmartz]

In azavea/climate-change-api#191 we instituted a rate limiter to prevent a single user from consuming too many system resources and denying other users access. Each user has a limit of 10 requests per minute, up to 5000 per day, and any requests after that limit has been reached fail with a HTTP 429 error. However, after the minute quota has cleared the blocked requests are perfectly OK to retry.

If a user has a report with more than 10 items or changes cities too frequently they are going to experience this problem, so we should ensure that the lab automatically retries requests that temporarily fail because of the user's quota.

[rmartz]

Close in favor of #327