tree-wide: panic when json marshalling fails

According to the new guidelines in docs/errors.md.

Note that this does not include code that marshals to a writer that
might fail (when a connection drops, for example).

cmd/osbuild-pipeline/main.go

@@ -141,7 +141,7 @@ func main() {
 		}
 		bytes, err = json.Marshal(rpmMDInfo)
 		if err != nil {
-			panic("could not marshal rpmmd struct into JSON")
+			panic(err)
 		}
 	} else {
 		manifest, err := imageType.Manifest(blueprint.Customizations, repos[arch.Name()], packageSpecs, buildPackageSpecs, imageType.Size(0))
@@ -151,7 +151,7 @@ func main() {
 
 		bytes, err = json.Marshal(manifest)
 		if err != nil {
-			panic("could not marshal manifest into JSON")
+			panic(err)
 		}
 	}
 	os.Stdout.Write(bytes)

cmd/osbuild-worker/main.go

@@ -102,7 +102,7 @@ func (c *ComposerClient) AddJob() (*jobqueue.Job, error) {
 	var b bytes.Buffer
 	err := json.NewEncoder(&b).Encode(request{})
 	if err != nil {
-		return nil, err
+		panic(err)
 	}
 	response, err := c.client.Post(c.createURL("/job-queue/v1/jobs"), "application/json", &b)
 	if err != nil {
@@ -129,7 +129,7 @@ func (c *ComposerClient) UpdateJob(job *jobqueue.Job, status common.ImageBuildSt
 	var b bytes.Buffer
 	err := json.NewEncoder(&b).Encode(&jobqueue.JobStatus{status, result})
 	if err != nil {
-		return err
+		panic(err)
 	}
 	urlPath := fmt.Sprintf("/job-queue/v1/jobs/%s/builds/%d", job.ID.String(), job.ImageBuildID)
 	url := c.createURL(urlPath)

internal/blueprint/blueprint.go

@@ -43,13 +43,13 @@ type Group struct {
 func (b *Blueprint) DeepCopy() (Blueprint, error) {
 	bpJSON, err := json.Marshal(b)
 	if err != nil {
-		return Blueprint{}, err
+		panic(err)
 	}
 
 	var bp Blueprint
 	err = json.Unmarshal(bpJSON, &bp)
 	if err != nil {
-		return Blueprint{}, err
+		panic(err)
 	}
 	return bp, nil
 }

internal/store/store.go

@@ -287,7 +287,6 @@ func (s *Store) change(f func() error) error {
 	if s.stateChannel != nil {
 		serialized, err := json.Marshal(s)
 		if err != nil {
-			// we ought to know all types that go into the store
 			panic(err)
 		}