Catch connectionreseterror error in image download

[wanliAlex]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  bug fix

• What is the current behavior? (You can also link to an open issue here)
  if an ConnectionResetError is raised, we will have 500 errors

• What is the new behavior (if this is a feature change)?
  we now catch it

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  no

• Have unit tests been run against this PR? (Has there also been any additional testing?)
  running

• Related Python client changes (link commit/PR here)
  no

• Related documentation changes (link commit/PR here)
  no

• Other information:
  no

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added / updated (for bug fixes / features)

[farshidz]

Look at thread results and raise an internal error (500) if a thread has failed so bugs in the threads aren't so hard to catch in the future