[tests] ProbackupTest::backup_node always requires valid 'node' object

[dmitry-lipetsk]

Hello,

If I understand correctly, ProbackupTest::backup_node allows node==None when data_dir is defined (see line 1098).

On the other side, this method always calls node.port (line 1110) and this is supposes that node is valid (not None).

pg_probackup/tests/helpers/ptrack_helpers.py

Lines 1091 to 1112 in a2510f5

	def backup_node(
	self, backup_dir, instance, node, data_dir=False,
	backup_type='full', datname=False, options=[],
	asynchronous=False, gdb=False,
	old_binary=False, return_id=True, no_remote=False,
	env=None
	):
	if not node and not data_dir:
	print('You must provide ether node or data_dir for backup')
	exit(1)
	if not datname:
	datname = 'postgres'
	cmd_list = [
	'backup',
	'-B', backup_dir,
	'--instance={0}'.format(instance),
	# "-D", pgdata,
	'-p', '%i' % node.port,
	'-d', datname
	]

---

I used a debugger to set None in node to "<some string>" in data_dir.

Expression if not node and not data_dir: said OK, but a test was finished with the following error:

        cmd_list = [
            'backup',
            '-B', backup_dir,
            '--instance={0}'.format(instance),
            # "-D", pgdata,
>           '-p', '%i' % node.port,
            '-d', datname
        ]
E       AttributeError: 'NoneType' object has no attribute 'port'

tests/helpers/ptrack_helpers.py:1110: AttributeError