gpfs has a minor bug in the use of charmhelpers

[Matt Bruzek]

I deployed the gpfs charm without an apt repository and it failed. The error message was not what I expected, and I believe it to be incorrect.

I was using the juju debug-hooks tool to run config-changed hook again.

# hooks/config-changed
Traceback (most recent call last):
  File "hooks/config-changed", line 69, in <module>
    hooks.execute(sys.argv)
  File "/var/lib/juju/agents/unit-gpfs-0/charm/lib/charmhelpers/core/hookenv.py", line 544, in execute
    self._hooks[hook_name]()
  File "hooks/config-changed", line 39, in config_changed
    gpfshooklib.check_empty_source(gpfs_url)
  File "/var/lib/juju/agents/unit-gpfs-0/charm/hooks/gpfshooklib.py", line 46, in check_empty_source
    "to install packages. See README for more info.", log.ERROR)
AttributeError: 'function' object has no attribute 'ERROR'

Looking at the charmhelpers/core/hookenv.py code I think it is trying to call the function named log. This is a minor difference and I believe it could be fixed.