More specific exceptions are raised when problems are encountered
looking up metadata and validating stream descriptor files, and
on the GUI those more specific exceptions are used to prevent
errors from being presented to the user.
If the user has selected the option to re-upload data for some
stream, blobs downloaded for that purpose will not be deleted
when they are finished being output. Instead, by default, for
the GUI they will be deleted when the stream is removed from
the GUI. That can be changed so they are not deleted at all,
using the lbry.conf file.
