Client parsing schema throws a horrible stacktrace when URL is incorrect

[luke-hill]

If you try parse a schema from a URL which is partially incorrect you get the horrible invalid token JSON error.

I found out sometimes this occurs due to not putting /graphql on the end of links. However this is inconsistent and doesn't always fix the issue (It did in my instance).

Perhaps we could find a way of throwing a better error. Also I'm getting this error when running a new query against this endpoint (And don't know why)