responseTooLarge reason is not output in R/request.r::signal_reason()

[ras44]

When querying a table that contains many fields, I will occasionally receive the ambiguous output:

Internal Error

An example:

  SELECT *
      FROM `bigquery-public-data.samples.github_timeline`

The issue occurs in R/request.r: results are retrieved from bq_get, which calls httr GET and finally process_request. The error that arises from process_request is passed to R/request.r::signal_reason, which signals a condition, but since this condition isn't handled, signal_reason ends with:

stop(message, call. = FALSE)

Unfortunately, the message output is uninformative, it only contains "Internal Error". Helpful information is contained in reason. In this case, it contains responseTooLarge.

This specific issue can be solved by reducing the page_size argument, however my point is that reason contains additional information that is useful for troubleshooting. Outputting reason and not just message in R/request::signal_reason.r would be helpful.

Another option is to handle the bigrquery_responseTooLarge class condition that is signaled, perhaps with a message recommending a smaller page_size argument.

[hadley]

Do you want to turn this into a PR? It would be helpful to include a link to the error API docs in a comment.