Pcs (and consequently and painfully, respective interactive execution to figure out the respective bash completion atoms) is not robust when it comes to keyboard interrupts

What I did:

```
$ pcs --
```

What I got (for instance):

```
File "/usr/sbin/pcs", line 6, in
from pkg_resources import load_entry_point
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3038, in
@_call_aside
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3022, in _call_aside
f(*args, **kwargs)
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3051, in _initialize_master_working_set
working_set = WorkingSet._build_master()
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 648, in _build_master
ws = cls()
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 641, in __init__
self.add_entry(entry)
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 697, in add_entry
for dist in find_distributions(entry, True):
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2033, in find_on_path
path_item, entry, metadata, precedence=DEVELOP_DIST
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2452, in from_location
py_version=py_version, platform=platform, **kw
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2792, in _reload_version
md_version = _version_from_file(self._get_metadata(self.PKG_INFO))
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2417, in _version_from_file
line = next(iter(version_lines), '')
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2584, in _get_metadata
if self.has_metadata(name):
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2624, in __getattr__
def __getattr__(self, attr):
KeyboardInterrupt
```

I.e. `/usr/sbin/pcs` needs to catch that exception from the very beginning
(ultimate solution for https://bugzilla.redhat.com/show_bug.cgi?id=1354498,
indeed, it should respond to it per the current context of use, but exit right
away when being run to complete something).

Start by reproducing the reported `pcs --` behavior and inspect the `/usr/sbin/pcs` entry point, including startup before the application loads. Determine how the KeyboardInterrupt should be handled for completion and interactive use; done means interruption no longer emits the shown traceback while the command exits appropriately.

Written by the indexing model from the issue text.