Description of problem:

Hi all,

Seems we need to fix some parts on Brocade FC driver after RHOSP 16 was rebased to RHEL 8 (and thus Python 3). The below error is raised when trying to attach a volume to an instance:

~~~
2020-06-15 21:11:46.907 129 INFO cinder.zonemanager.drivers.brocade.brcd_rest_fc_zone_client [req-49af2a3b-a31a-4a87-8bee-d9ba262764c0 7bc4473b43ef45dbbd70da0755e47959 1fc8348718564464a3fd56b321d88634 - default default] REST logout success
2020-06-15 21:11:46.908 129 INFO cinder.zonemanager.drivers.brocade.brcd_fc_zone_driver [req-49af2a3b-a31a-4a87-8bee-d9ba262764c0 7bc4473b43ef45dbbd70da0755e47959 1fc8348718564464a3fd56b321d88634 - default default] Filtered targets for SAN
 is: <filter object at 0x7effa1bac710>
2020-06-15 21:11:46.908 129 ERROR cinder.zonemanager.fc_zone_manager [req-49af2a3b-a31a-4a87-8bee-d9ba262764c0 7bc4473b43ef45dbbd70da0755e47959 1fc8348718564464a3fd56b321d88634 - default default] Failed adding connection for fabric=None: E
rror: 'filter' object is not subscriptable
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager [req-49af2a3b-a31a-4a87-8bee-d9ba262764c0 7bc4473b43ef45dbbd70da0755e47959 1fc8348718564464a3fd56b321d88634 - default default] Driver initialize connection failed (error: Fibre Channe
l connection control failure: Failed adding connection for fabric=None: Error: 'filter' object is not subscriptable).: cinder.exception.ZoneManagerException: Fibre Channel connection control failure: Failed adding connection for fabric=Non
e: Error: 'filter' object is not subscriptable
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager Traceback (most recent call last):
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/zonemanager/fc_zone_manager.py", line 223, in add_connection
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     fabric_map = self.get_san_context(target_list)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/zonemanager/fc_zone_manager.py", line 335, in get_san_context
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     fabric_map = self.driver.get_san_context(target_wwn_list)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/zonemanager/drivers/brocade/brcd_fc_zone_driver.py", line 450, in get_san_context
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     visible_targets[idx]).replace(':', '')
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager TypeError: 'filter' object is not subscriptable
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager 
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager During handling of the above exception, another exception occurred:
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager 
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager Traceback (most recent call last):
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/volume/manager.py", line 4490, in _connection_create
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     conn_info = self.driver.initialize_connection(volume, connector)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/volume/drivers/pure.py", line 175, in wrapper
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     result = f(*args, **kwargs)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/volume/drivers/pure.py", line 2659, in initialize_connection
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     fczm_utils.add_fc_zone(properties)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/zonemanager/utils.py", line 86, in add_fc_zone
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     zm.add_connection(connection_info)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager   File "/usr/lib/python3.6/site-packages/cinder/zonemanager/fc_zone_manager.py", line 248, in add_connection
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager     raise exception.ZoneManagerException(reason=msg)
2020-06-15 21:11:46.908 129 ERROR cinder.volume.manager cinder.exception.ZoneManagerException: Fibre Channel connection control failure: Failed adding connection for fabric=None: Error: 'filter' object is not subscriptable
~~~

It looks like the code is expecting filter() to return a list. While it was fine with Python 2, since version 3 the iterations are returned, as described here:

https://docs.python.org/3.0/whatsnew/3.0.html#views-and-iterators-instead-of-lists

---8<---
Some well-known APIs no longer return lists:

- dict methods dict.keys(), dict.items() and dict.values() return “views” instead of lists. For example, this no longer works: k = d.keys(); k.sort(). Use k = sorted(d) instead (this works in Python 2.5 too and is just as efficient).
- Also, the dict.iterkeys(), dict.iteritems() and dict.itervalues() methods are no longer supported.
--> - map() and filter() return iterators. If you really need a list, a quick fix is e.g. list(map(...)), but a better fix is often to use a list comprehension (especially when the original code uses lambda), or rewriting the code so it doesn’t need a list at all. Particularly tricky is map() invoked for the side effects of the function; the correct transformation is to use a regular for loop (since creating a list would just be wasteful).
- range() now behaves like xrange() used to behave, except it works with values of arbitrary size. The latter no longer exists.
- zip() now returns an iterator.
--->8---


Version-Release number of selected component (if applicable):

python3-cinder-15.0.2-0.20200123220928.900f769.el8ost.noarch.rpm:

~~~
rpm -qlp ./python3-cinder-15.0.2-0.20200123220928.900f769.el8ost.noarch.rpm  | egrep "fc_zone_manager.py|brcd_fc_zone_driver.py"

/usr/lib/python3.6/site-packages/cinder/zonemanager/drivers/brocade/brcd_fc_zone_driver.py
/usr/lib/python3.6/site-packages/cinder/zonemanager/fc_zone_manager.py
~~~