Adjust error messages as per discussion in #557

internals/daemon/api_changes.go

@@ -243,7 +243,7 @@ func v1PostChange(c *Command, r *http.Request, _ *UserState) Response {
 	}
 
 	if reqData.Action != "abort" {
-		return BadRequest("change action %q is unsupported", reqData.Action)
+		return BadRequest("invalid action %q", reqData.Action)
 	}
 
 	if chg.Status().Ready() {

internals/daemon/api_checks.go

@@ -89,7 +89,7 @@ func v1PostChecks(c *Command, r *http.Request, _ *UserState) Response {
 		}
 	default:
 		if len(payload.Checks) == 0 {
-			return BadRequest("no checks to %s provided", payload.Action)
+			return BadRequest("must specify checks for %s action", payload.Action)
 		}
 	}
 
@@ -104,7 +104,7 @@ func v1PostChecks(c *Command, r *http.Request, _ *UserState) Response {
 	case "stop":
 		checks, err = checkmgr.StopChecks(plan, payload.Checks)
 	default:
-		return BadRequest("action %q is unsupported", payload.Action)
+		return BadRequest("invalid action %q", payload.Action)
 	}
 	if err != nil {
 		return BadRequest("cannot %s checks: %v", payload.Action, err)

internals/daemon/api_services.go

@@ -95,7 +95,7 @@ func v1PostServices(c *Command, r *http.Request, _ *UserState) Response {
 		payload.Services = services
 	default:
 		if len(payload.Services) == 0 {
-			return BadRequest("no services to %s provided", payload.Action)
+			return BadRequest("must specify services for %s action", payload.Action)
 		}
 	}
 
@@ -182,7 +182,7 @@ func v1PostServices(c *Command, r *http.Request, _ *UserState) Response {
 		sort.Strings(services)
 		payload.Services = services
 	default:
-		return BadRequest("action %q is unsupported", payload.Action)
+		return BadRequest("invalid action %q", payload.Action)
 	}
 	if err != nil {
 		return BadRequest("cannot %s services: %v", payload.Action, err)