Description of problem:
The following utility method incorrectly parses multipath errors as a device name :

cinder/brick/initiator/connector.py

~~~
473     def _get_multipath_device_name(self, single_path_device):
474         device = os.path.realpath(single_path_device)
475         out = self._run_multipath(['-ll',
476                                   device],
477                                   check_exit_code=[0, 1])[0]
478         mpath_line = [line for line in out.splitlines()
479                       if "scsi_id" not in line]  # ignore udev errors
480         if len(mpath_line) > 0 and len(mpath_line[0]) > 0:
481             return "/dev/mapper/%s" % mpath_line[0].split(" ")[0]
482 
483         return None
~~~

This results in the following error, this later escalates into an odd encoding exception slightly masking this original failure :

~~~
12701 2015-06-18 17:00:06.656 1228 DEBUG cinder.brick.initiator.connector [req-c5ed9a90-c0de-44bb-a602-7d7168c51180 916f3ee5132143dbb723231472118a22 7b1de946cd814605aaca2082ffc650c7 - - -] multipath ['-ll', u'/dev/sdv']: stdout=Jun 18 17:00:06 | vda: No fc_host device for 'host-1'
12702 Jun 18 17:00:06 | vda: No fc_host device for 'host-1'
12703 Jun 18 17:00:06 | vda: No fc_remote_port device for 'rport--1:-1-0'
12704 mpathe (3624a9370f5786ee930acb2bc00011075) dm-5 PURE    ,FlashArray
12705 size=20G features='0' hwhandler='0' wp=rw
12706 |-+- policy='service-time 0' prio=1 status=active
12707 | `- 7:0:0:6  sdv 65:80  active ready running
12708 |-+- policy='service-time 0' prio=1 status=enabled
12709 | `- 10:0:0:6 sdu 65:64  active ready running
12710 |-+- policy='service-time 0' prio=1 status=enabled
12711 | `- 9:0:0:6  sdw 65:96  active ready running
12712 `-+- policy='service-time 0' prio=1 status=enabled
12713   `- 8:0:0:6  sdx 65:112 active ready running
12714  stderr= _run_multipath /usr/lib/python2.7/site-packages/cinder/brick/initiator/connector.py:607
12715 2015-06-18 17:00:06.656 1228 DEBUG cinder.openstack.common.processutils [req-c5ed9a90-c0de-44bb-a602-7d7168c51180 916f3ee5132143dbb723231472118a22 7b1de946cd814605aaca2082ffc650c7 - - -] Running cmd (subprocess): sudo cinder-rootwrap /etc/cinder/rootwrap.conf dd if=/dev/mapper/Jun of=/dev/null count=1 execute /usr/lib/python2.7/site-packages/cinder/openstack/common/processutils.py:158
~~~

Version-Release number of selected component (if applicable):
openstack-cinder-2014.2.3-5.el7ost.noarch

How reproducible:
Always.

Steps to Reproduce:
1. Use a multipath enabled backend such as the currently uncertified `PureStorage` backend.
2. Ensure `multipath -ll` prints some form of error or warning on the first line.
3. Attempt to attach a volume using the above backend.

Actual results:
Attaching the volume fails as the error string is parsed as the device name.

Expected results:
Error string ignored and the volume is attached.

Additional info:

Simple workaround is to remove errors such as the above by blacklisting local devices etc.

I have a simple patch in mind for this to reuse the linuxscsi utility methods I've been working on, I'll push this upstream to os-brick shortly and into cinder for stable/kilo.