Prevent stack trace if token is expired

Handle the expired token error properly to avoid a stack trace.

(We should return a better error - this can be done in the future
by modifying the request handler.)

internal/datasources/system/data_source.go

@@ -86,6 +86,12 @@ func getSystemByName(
 		Systems().
 		GetAsSystemsGetResponse(ctx, grc)
 
+	if err != nil {
+		tflog.Error(ctx, "failed to get system by name: "+name)
+
+		return nil, err
+	}
+
 	if systems.GetTotal() == nil {
 		msg := "total is nil"
 		tflog.Error(ctx, msg)

internal/simulator/system.go

@@ -19,9 +19,19 @@ func simulateSystemGetByName() {
 	gock.New("http://localhost").
 		Get("/private-cloud-business/v1beta1/systems").
 		MatchParam("filter", "name eq "+systemName).
+		MatchHeader("Authorization", "Bearer abcdefghijklmnopqrstuvwxyz-0123456789").
 		Reply(200).
 		SetHeader("Content-Type", "application/json").
 		BodyString(systemsByName)
+
+	gock.New("http://localhost").
+		Get("/private-cloud-business/v1beta1/systems").
+		MatchParam("filter", "name eq "+systemName).
+		MatchHeader("Authorization", "Bearer expired-token").
+		Reply(401).
+		SetHeader("Content-Type", "text/plain").
+		BodyString("Jwt is not in the form of Header.Payload.Signature " +
+			"with two dots and 3 sections")
 }
 
 func System() {

test/system/system_test.go

@@ -119,3 +119,44 @@ func TestAccSystemDataSourceMissingName(t *testing.T) {
 		},
 	})
 }
+
+func TestAccSystemDataSourceBadAuth(t *testing.T) {
+	providerConfigBadAuth := `
+terraform {
+  required_providers {
+    hpegl = {
+      source = "github.com/HewlettPackard/hpegl-pcbe-terraform-resources"
+    }
+  }
+}
+
+provider "hpegl" {
+        pc {
+                host            = "http://localhost:8080"
+                token           = "expired-token"
+
+                http_dump       = true
+                poll_interval   = 0.001
+                max_polls       = 10
+        }
+}
+`
+	config := providerConfigBadAuth + `
+	data "hpegl_pc_system" "test" {
+		name = "array-5305-grp"
+	}
+	`
+	// TODO: return more informative error message - including
+	// http response code (requires change to request handler)
+	expected := `text does not support structured data`
+	resource.Test(t, resource.TestCase{
+		ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
+		Steps: []resource.TestStep{
+			{
+				Config:      config,
+				ExpectError: regexp.MustCompile(expected),
+				PlanOnly:    true,
+			},
+		},
+	})
+}