Added vSphere machine driver

Signed-off-by: Fabio Rapposelli <frapposelli@vmware.com>

drivers/vmwarevsphere/errors/datastore_error.go

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2014 VMware, Inc.  All rights reserved.  Licensed under the Apache v2 License.
+ */
+
+package errors
+
+import "fmt"
+
+type DatastoreError struct {
+	datastore string
+	operation string
+	reason    string
+}
+
+func NewDatastoreError(datastore, operation, reason string) error {
+	err := DatastoreError{
+		datastore: datastore,
+		operation: operation,
+		reason:    reason,
+	}
+	return &err
+}
+
+func (err *DatastoreError) Error() string {
+	return fmt.Sprintf("Unable to %s on datastore %s due to %s", err.operation, err.datastore, err.reason)
+}