Add an Exception instance to QueryError

[jfischoff]

In varying contexts I would like to be able to use throwIO with QueryError. Instead of wrapping it a newtype I would prefer if there was a Exception instance already defined. I think the default instance would be fine.

So the changes would be:

data QueryError =
  QueryError ByteString [Text] CommandError
  deriving (Show, Eq, Typeable)

instance Exception QueryError

I don't think this will break code nor will it incur an additional dependency.

[nikita-volkov]

Although I feel opposed to this since I consider the presence of exceptions in Haskell altogether a mistake, this is not the first time I get this request. So okay, let's do this! Can you make a PR?

[jfischoff]

Yep. I'll make a PR.

I get the dislike of exceptions. I find them useful in tests.

[mitchellwrosen]

Can this be closed?

[nikita-volkov]

Yep. Thanks. QueryError has an Exception instance now.