Don't break when volume binds contain unicode characters

[shin-]

Also includes a few unit tests for utils.convert_volume_binds

Fixes #782

[aanand]

Might be able to avoid this step if we go:

expected = [six.u('/mnt/지연:/unicode/박:rw')]

[shin-]

@aanand Thanks, didn't know about six.u. PTAL?

[aanand]

Cool. Perhaps the first test should be rewritten so it tests byte string input on all Python versions:

    def test_convert_volume_bindings_binary_input(self):
        expected = [six.u('/mnt/지연:/unicode/박:rw')]

        data = {
            b'/mnt/지연': {
                'bind': b'/unicode/박',
                'mode': 'rw'
            }
        }
        self.assertEqual(
            convert_volume_binds(data), expected
        )

[shin-]

Okay, I've tried all sorts of combination, I've settled on just separating py2 and py3 tests completely (so it's 2+2 now). On the bright side, results were consistent all along (and we have tests to prove it)!

[aanand]

OK, I see the rationale, but instead of entirely separate test methods, could we just switch on the Python version inside the method?

def test_convert_volume_binds_unicode_bytes_input(self):
    if six.PY2:
        expected = [unicode('/mnt/지연:/unicode/박:rw', 'utf-8')]
        data = {
            '/mnt/지연': {
                'bind': '/unicode/박',
                'mode': 'rw'
            }
        }
    else:
        expected = ['/mnt/지연:/unicode/박:rw']
        data = {
            bytes('/mnt/지연', 'utf-8'): {
                'bind': bytes('/unicode/박', 'utf-8'),
                'mode': 'rw'
            }
        }

    self.assertEqual(convert_volume_binds(data), expected)

def test_convert_volume_binds_unicode_unicode_input(self):
    if six.PY2:
        expected = [unicode('/mnt/지연:/unicode/박:rw', 'utf-8')]
        data = {
            unicode('/mnt/지연', 'utf-8'): {
                'bind': unicode('/unicode/박', 'utf-8'),
                'mode': 'rw'
            }
        }
    else:
        expected = ['/mnt/지연:/unicode/박:rw']
        data = {
            '/mnt/지연': {
                'bind': '/unicode/박',
                'mode': 'rw'
            }
        }

    self.assertEqual(convert_volume_binds(data), expected)