core, eth, les, rpc: polish catalyst errors, add context

rpc/errors.go

@@ -54,7 +54,6 @@ var (
 	_ Error = new(invalidRequestError)
 	_ Error = new(invalidMessageError)
 	_ Error = new(invalidParamsError)
-	_ Error = new(CustomError)
 )
 
 const defaultErrorCode = -32000
@@ -102,12 +101,3 @@ type invalidParamsError struct{ message string }
 func (e *invalidParamsError) ErrorCode() int { return -32602 }
 
 func (e *invalidParamsError) Error() string { return e.message }
-
-type CustomError struct {
-	Code            int
-	ValidationError string
-}
-
-func (e *CustomError) ErrorCode() int { return e.Code }
-
-func (e *CustomError) Error() string { return e.ValidationError }