[bug] improve error message on blob download error

The previous error message had some problems:

- the connection should not be a problem, as this is going over TCP. If
  the HTTP request was succesful, there's no reason to think its
  contents could have been corrupted by a connection problem.

- I am not sure what's the best communication strategy here, but the
  real problem is either a bug or actual tampering, so i make this
  explicit.

- A problem like this should be reported always, not only when the
  problem persists.

0 files changed, 0 insertions, 0 deletions