Description of problem:

lvm exceptions not caught/handled when in midst of transaction.

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

Installed Packages
Name        : yum
Arch        : noarch
Version     : 3.4.3
Release     : 132.el7
Size        : 5.5 M
Repo        : installed
From repo   : RHEL-7.2
Summary     : RPM package installer/updater/manager

How reproducible:

Always, in a sense. That is, if raised, exceptions will not be caught, AFAICT. On the other hand, creating the conditions that cause a specific exception to be raised isn't that easy.

Steps to Reproduce:
1. I did a bunch of things that finally resulted in a stack trace. They were a complicated sequence of downgrades and upgrades using local repos, and I'm not even sure that they were the root of the problem. However, they did cause an exception to be raised.
2. I observed a stack trace:

Running transaction
Traceback (most recent call last):
  File "/usr/bin/yum", line 29, in <module>
    yummain.user_main(sys.argv[1:], exit_code=True)
  File "/usr/share/yum-cli/yummain.py", line 365, in user_main
    errcode = main(args)
  File "/usr/share/yum-cli/yummain.py", line 271, in main
    return_code = base.doTransaction()
  File "/usr/share/yum-cli/cli.py", line 773, in doTransaction
    resultobject = self.runTransaction(cb=cb)
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 1736, in runTransaction
    if self.fssnap.available and ((self.conf.fssnap_automatic_pre or
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 1126, in <lambda>
    fssnap = property(fget=lambda self: self._getFSsnap(),
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 1062, in _getFSsnap
    devices=devices)
  File "/usr/lib/python2.7/site-packages/yum/fssnapshots.py", line 158, in __init__
    self._vgnames = _list_vg_names() if self.available else []
  File "/usr/lib/python2.7/site-packages/yum/fssnapshots.py", line 56, in _list_vg_names
    names = lvm.listVgNames()
lvm.LibLVMError: (-1, 'Request to list VGs in lvmetad failed after device filter mismatch.')

3. A quick look at the source seems to indicate that lvm raised exceptions aren't being caught.

Actual results:

Stack trace in middle of transaction.

Expected results:

Better handling of lvm exceptions, especially in this case where there is a check for the result being the empty list already and especially when it occurs in the
middle of a transaction (which are generally considered important not to fail).

Additional info:

None.