##### SUMMARY
Customer request: When typing the string to encrypt, it shows up as plain text. Since the string is being encrypted, it's safe to assume that it's sensitive (e.g. passwords) and should therefore be hidden. At the very least, maybe this could be a command line option. If it is hidden, I'd prefer to be forced to enter it twice to avoid mismatch. To mitigate this issue, I am currently using "stty -echo", but that shouldn't be necessary.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
ansible-vault
edit_parser = subparsers.add_parser('edit', help='Edit vault encrypted file', parents=[vault_id, common])
        edit_parser.set_defaults(func=self.execute_edit)
        edit_parser.add_argument('args', help='Filename', metavar='file_name', nargs='*')
        view_parser = subparsers.add_parser('view', help='View vault encrypted file', parents=[common])
        view_parser.set_defaults(func=self.execute_view)
        view_parser.add_argument('args', help='Filename', metavar='file_name', nargs='*')
        encrypt_parser = subparsers.add_parser('encrypt', help='Encrypt YAML file', parents=[common, output, vault_id])
        encrypt_parser.set_defaults(func=self.execute_encrypt)
        encrypt_parser.add_argument('args', help='Filename', metavar='file_name', nargs='*')
        enc_str_parser = subparsers.add_parser('encrypt_string', help='Encrypt a string', parents=[common, output, vault_id])
        enc_str_parser.set_defaults(func=self.execute_encrypt_string)
        enc_str_parser.add_argument('args', help='String to encrypt', metavar='string_to_encrypt', nargs='*')
        enc_str_parser.add_argument('-p', '--prompt', dest='encrypt_string_prompt',
                                    action='store_true',
                                    help="Prompt for the string to encrypt")
        enc_str_parser.add_argument('-n', '--name', dest='encrypt_string_names',
                                    action='append',
                                    help="Specify the variable name")
        enc_str_parser.add_argument('--stdin-name', dest='encrypt_string_stdin_name',
                                    default=None,
                                    help="Specify the variable name for stdin")
        rekey_parser = subparsers.add_parser('rekey', help='Re-key a vault encrypted file', parents=[common, vault_id])
        rekey_parser.set_defaults(func=self.execute_rekey)
        rekey_new_group = rekey_parser.add_mutually_exclusive_group()
        rekey_new_group.add_argument('--new-vault-password-file', default=None, dest='new_vault_password_file',
                                     help="new vault password file for rekey", type=opt_help.unfrack_path())
        rekey_new_group.add_argument('--new-vault-id', default=None, dest='new_vault_id', type=str,
                                     help='the new vault identity to use for rekey')
        rekey_parser.add_argument('args', help='Filename', metavar='file_name', nargs='*')
    def post_process_args(self, options):