Vassilii Khachaturov:

Vassilii Khachaturov:

* in some cases more specific sg exception types were used in place
  of the more generic one, e.g., sg_io_exception instead of sg_exception
  when the context of the error was an IO error
* in some cases, the error message was made more specific
* minor style fix for exception rethrowing --- using throw; whenever
  a re-throw is made; sometimes optimizing away the exception symbol name
  in the catch handler at all
* more specific catch handlers added in some places -- e.g.,
  an sg_io_exception caught ahead of sg_exception