I had the same problem.
And cause of the Framework I'm using I couldn't catch the Exception directly. The namespace was wrong.
I just added a backslash before into
catch (\Exception $err)
and it got the right Exception!
Maybe the cause was that the CurlException's parent is RequestException, that has itself \RuntimeException as parent.
So if you want to catch the parent Exception you need to add the backslash as well.
Don't ask me a deep explanation of that. I'm just supposing.
And probably you already solved the error after so many months ;)