Occasional KeyError on /index/summary endpoint

[theathorn]

Not sure of the steps to generate this, but I selected the DCP2 Catalog, file type as "unspecified" then clicked on something and got:

[hannes-ucsc]

I don't think this is caused by what @theathorn was doing at the time but rather a random race condition. The summary endpoint runs three or so requests in parallel and that exposes a thread-safety issue with boto3 sessions: boto/boto3#1592

[theathorn]

From @kbergin : Got this error when trying to do a handoff from dcp2.data.humancellatlas.org. I selected a project and clicked the export button and it gave me this error. I hit the back button then clicked it again and got the export selection page with no error.