Send email when runner usage CSV export results in error

The following discussions from !139158 (merged) should be addressed:

• @hfyngvason started a discussion:

  Not a blocker: If the user requests an export, and they are waiting for it but an error occurs, how will they know it failed? Would it make sense to notify them either way?

• @hfyngvason started a discussion:

  Can we also test that the attachment is there? This seems like the most important part of the email.