Description of problem:

Before 4.2, it was possible to the documentation for vdsm configuration file
by running vdsm/config.py as a script:

    python /usr/lib/python2.7/site-packages/vdsm/common/config.py

This fails now with this error:

# python /usr/lib/python2.7/site-packages/vdsm/common/config.py
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/common/config.py", line 739, in <module>
    config = load('vdsm')
  File "/usr/lib/python2.7/site-packages/vdsm/common/config.py", line 711, in load
    read_configs(cfg, name)
  File "/usr/lib/python2.7/site-packages/vdsm/common/config.py", line 733, in read_configs
    dropins.extend(glob.glob(pattern))
AttributeError: 'module' object has no attribute 'glob'

The issue is the new vdsm/common/glob.py module, added in:

commit fd13ee1e55d61f06516ad10c890470a2c822b9c8
Author: Idan Shaby <ishaby>
Date:   Thu Jan 12 18:43:56 2017 +0200

    compat: add glob.escape from Python 3.6
    
    glob.escape was added in Python 3.6.
    Since we need it for escaping values that are passed to glob.glob,
    this patch adds it to glob.py.
    
    Change-Id: Id2989a9edcc87ec671d8c29ec7900e01b537b3f1
    Related-To: https://bugzilla.redhat.com/1302358
    Signed-off-by: Idan Shaby <ishaby>

But having a glob.py module in vdsm is correct; we use absolute
imports, so this module does not hide the python stdlib glob module.
In vdsm, we import our private glob with:

   from vdsm.common import glob

So the real issue is running config.py as a script - this is not a reliable
way to print configuration, since running a script change PYTHONPATH
to include the directory where the script is located, and this hides
the python builtin glob module.

The right way to print the configuration is:

# python -c "from vdsm.common import config; config.print_config()"

# VDSM Sample Configuration

[vars]

# Enable core dump.
# core_dump_enable = true

# Reserves memory for the host to prevent VMs from using all the
# physical pages. The values are in Mbytes.
# host_mem_reserve = 256
...


Version-Release number of selected component (if applicable):
vdsm > 4.19.10

How reproducible:
Always

Steps to Reproduce:
1. Run:

    python /usr/lib/python2.7/site-packages/vdsm/common/config.py


I think the best way to resolve this would be to convert config.py to regular
module, so it is not possible to run it as a script.

If the feature of printing the configuration is important enough, it should be
provided by "vdsm-tool show-default-config".