Make CLI functions return error instead of fatal out (#1379)

Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse 
the functions nor writing unit tests. This PR aims to make functions 
return errors instead of error out.

pkg/fission-cli/cmd/spec/init.go

@@ -23,11 +23,11 @@ import (
 	"path/filepath"
 
 	"github.com/ghodss/yaml"
+	"github.com/pkg/errors"
 	uuid "github.com/satori/go.uuid"
 
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
 	spectypes "github.com/fission/fission/pkg/fission-cli/cmd/spec/types"
 	"github.com/fission/fission/pkg/fission-cli/util"
 )
@@ -38,8 +38,12 @@ type InitSubCommand struct {
 }
 
 func Init(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := InitSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }
@@ -54,13 +58,15 @@ func (opts *InitSubCommand) do(flags cli.Input) error {
 
 func (opts *InitSubCommand) complete(flags cli.Input) error {
 	// Figure out spec directory
-	specDir := cmd.GetSpecDir(flags)
+	specDir := util.GetSpecDir(flags)
 
 	name := flags.String("name")
 	if len(name) == 0 {
 		// come up with a name using the current dir
 		dir, err := filepath.Abs(".")
-		util.CheckErr(err, "get current working directory")
+		if err != nil {
+			return errors.Wrap(err, "error getting current working directory")
+		}
 		basename := filepath.Base(dir)
 		name = util.KubifyName(basename)
 	}
@@ -73,7 +79,9 @@ func (opts *InitSubCommand) complete(flags cli.Input) error {
 	// Create spec dir
 	fmt.Printf("Creating fission spec directory '%v'\n", specDir)
 	err := os.MkdirAll(specDir, 0755)
-	util.CheckErr(err, fmt.Sprintf("create spec directory '%v'", specDir))
+	if err != nil {
+		return errors.Wrapf(err, "create spec directory '%v'", specDir)
+	}
 
 	// Write the deployment config
 	opts.deployConfig = &spectypes.DeploymentConfig{
@@ -94,7 +102,7 @@ func (opts *InitSubCommand) complete(flags cli.Input) error {
 // run just initializes an empty spec directory and adds some
 // sample YAMLs in there that might be useful.
 func (opts *InitSubCommand) run(flags cli.Input) error {
-	specDir := cmd.GetSpecDir(flags)
+	specDir := util.GetSpecDir(flags)
 
 	// Add a bit of documentation to the spec dir here
 	err := ioutil.WriteFile(filepath.Join(specDir, "README"), []byte(SPEC_README), 0644)
@@ -103,7 +111,9 @@ func (opts *InitSubCommand) run(flags cli.Input) error {
 	}
 
 	err = writeDeploymentConfig(specDir, opts.deployConfig)
-	util.CheckErr(err, "write deployment config")
+	if err != nil {
+		return errors.Wrap(err, "error writing deployment config")
+	}
 
 	// Other possible things to do here:
 	// - add example specs to the dir to make it easy to manually