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[Sean Dague <sean@xxxxxxxxx>]

this is an oslo issue, it's in openstack/ namespace

** Also affects: oslo-incubator
   Importance: Undecided
       Status: New

** Changed in: oslo-incubator
       Status: New => Confirmed

** No longer affects: nova

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https://bugs.launchpad.net/bugs/1297261

Title:
  messages when the module import fails are very misleading and not
  descriptive

Status in The Oslo library incubator:
  Confirmed

Bug description:
  I had problem to import vmware module due to lack of it's dep. The
  message in log though was saying that there is no vmware module, which
  is far from true. The problematic code is at least:

  /usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py

  def import_class(import_str):
  ...
      try:
          __import__(mod_str)
          return getattr(sys.modules[mod_str], class_str)
      except (ValueError, AttributeError):
          raise ImportError('Class %s cannot be found (%s)' %
                            (class_str,
                             traceback.format_exception(*sys.exc_info())))

  Which would obfuscate the error message when some module import dies
  on ValueError, and:

  
  def import_object_ns(name_space, import_str, *args, **kwargs):
      """Tries to import object from default namespace.

      Imports a class and return an instance of it, first by trying
      to find the class in a default namespace, then failing back to
      a full path if not found in the default namespace.
      """
      import_value = "%s.%s" % (name_space, import_str)
      try:
          return import_class(import_value)(*args, **kwargs)
      except ImportError:
          return import_class(import_str)(*args, **kwargs)

  Which will say ImportError: Missing module import_str, but only as a
  result of failure of the first import in the try-except block,
  effectively hiding the true reason of the failure.

  In other words, if the first import fails for some interesting
  reasons, some other, possible meaningles import is tried and only it's
  error is let to propagate.

  
  +++ This bug was initially created as a clone of Bug #1080424 +++

  Description of problem:
  When having nova-compute alone on a node, I cannot start it (using PYTHONVERBOSE=1 and slightly modified init script for debuging purposes):

  2014-03-25 11:10:42.153 10009 INFO nova.virt.driver [-] Loading compute driver 'vmwareapi.VMwareVCDriver'
  import nova.virt.vmwareapi # directory /usr/lib/python2.6/site-packages/nova/virt/vmwareapi
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/__init__.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/__init__.py
  import nova.virt.vmwareapi # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/__init__.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/driver.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/driver.py
  import nova.virt.vmwareapi.driver # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/driver.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/error_util.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/error_util.py
  import nova.virt.vmwareapi.error_util # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/error_util.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/host.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/host.py
  import nova.virt.vmwareapi.host # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/host.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim_util.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim_util.py
  import nova.virt.vmwareapi.vim_util # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim_util.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vm_util.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vm_util.py
  import nova.virt.vmwareapi.vm_util # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vm_util.pyc
  # /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim.pyc matches /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim.py
  import nova.virt.vmwareapi.vim # precompiled from /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim.pyc
  2014-03-25 11:10:42.155 10009 ERROR nova.virt.driver [-] Unable to load the virtualization driver
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver Traceback (most recent call last):
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver   File "/usr/lib/python2.6/site-packages/nova/virt/driver.py", line 1115, in load_compute_driver
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver     virtapi)
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver   File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 54, in import_object_ns
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver     return import_class(import_str)(*args, **kwargs)
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver   File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 30, in import_class
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver     __import__(mod_str)
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver ImportError: No module named vmwareapi
  2014-03-25 11:10:42.155 10009 TRACE nova.virt.driver 

  
  when trying to imprort it in ipython:
  In [1]: import nova.virt.vmwareapi
  ---------------------------------------------------------------------------
  ImportError                               Traceback (most recent call last)
  <ipython-input-1-c0f052a58780> in <module>()
  ----> 1 import nova.virt.vmwareapi

  /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/__init__.py in <module>()
       19 """
       20 # NOTE(sdague) for nicer compute_driver specification
  ---> 21 from nova.virt.vmwareapi import driver
       22 
       23 VMwareESXDriver = driver.VMwareESXDriver

  /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/driver.py in <module>()
       37 from nova.virt.vmwareapi import error_util
       38 from nova.virt.vmwareapi import host
  ---> 39 from nova.virt.vmwareapi import vim
       40 from nova.virt.vmwareapi import vim_util
       41 from nova.virt.vmwareapi import vm_util

  /usr/lib/python2.6/site-packages/nova/virt/vmwareapi/vim.py in <module>()
       25 
       26 from oslo.config import cfg
  ---> 27 import suds
       28 
       29 from nova.openstack.common.gettextutils import _

  ImportError: No module named suds


  
  Version-Release number of selected component (if applicable):
  openstack-nova-compute-2013.2.2-2.el6ost.noarch
  python-nova-2013.2.2-2.el6ost.noarch

  How reproducible:
  always

  Steps to Reproduce:
  1. Install nova-compute
  2. do the import in the python interpret

  
  Actual results:
  ImportError: No module named suds

  Expected results:
  no problem

  Additional info:

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