Move cncd/pipeline/pipeline/ to pipeline/ (#347)

* Refactor: move cncd/pipeline/ to pipeline/

* Refactor: move pipeline/pipeline/ to pipeline/

pipeline/error.go

@@ -0,0 +1,38 @@
+package pipeline
+
+import (
+	"errors"
+	"fmt"
+)
+
+var (
+	// ErrSkip is used as a return value when container execution should be
+	// skipped at runtime. It is not returned as an error by any function.
+	ErrSkip = errors.New("Skipped")
+
+	// ErrCancel is used as a return value when the container execution receives
+	// a cancellation signal from the context.
+	ErrCancel = errors.New("Cancelled")
+)
+
+// An ExitError reports an unsuccessful exit.
+type ExitError struct {
+	Name string
+	Code int
+}
+
+// Error returns the error message in string format.
+func (e *ExitError) Error() string {
+	return fmt.Sprintf("%s : exit code %d", e.Name, e.Code)
+}
+
+// An OomError reports the process received an OOMKill from the kernel.
+type OomError struct {
+	Name string
+	Code int
+}
+
+// Error reteurns the error message in string format.
+func (e *OomError) Error() string {
+	return fmt.Sprintf("%s : received oom kill", e.Name)
+}