http: cleanup http related errors

We don't need to return information about the actual HTTP error. That's usually
not something the user cares about (and is usually implied from the command).

This way, we get an actual context canceled error when the context is canceled.

http/client.go

@@ -88,7 +88,14 @@ func (c *client) Execute(req *cmds.Request, re cmds.ResponseEmitter, env cmds.En
 
 	res, err := c.send(req)
 	if err != nil {
-		if isConnRefused(err) {
+		// Unwrap any URL errors. We don't really need to expose the
+		// underlying HTTP nonsense to the user.
+		if urlerr, ok := err.(*url.Error); ok {
+			err = urlerr.Err
+		}
+
+		if netoperr, ok := err.(*net.OpError); ok && netoperr.Op == "dial" {
+			// Connection refused.
 			if c.fallback != nil {
 				// XXX: this runs the PreRun twice
 				return c.fallback.Execute(req, re, env)
@@ -237,17 +244,3 @@ func getQuery(req *cmds.Request) (string, error) {
 
 	return query.Encode(), nil
 }
-
-func isConnRefused(err error) bool {
-	// unwrap url errors from http calls
-	if urlerr, ok := err.(*url.Error); ok {
-		err = urlerr.Err
-	}
-
-	netoperr, ok := err.(*net.OpError)
-	if !ok {
-		return false
-	}
-
-	return netoperr.Op == "dial"
-}