Improve capabilities module by detecting /sbin/getcap error message and stop early with a meaningful error message (#10455)

* modules/capabilities.py: fail & propagate if getcap command error

* Fix comment spacing (pep8)

* Add changelogs fragment for PR 10455

* Update changelogs/fragments/10455-capabilities-improve-error-detection.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: clement rouault <clement.rouault@exatrack.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

changelogs/fragments/10455-capabilities-improve-error-detection.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - capabilities - using invalid path (symlink/directory/...) returned unrelated and incoherent error messages (https://github.com/ansible-collections/community.general/issues/5649, https://github.com/ansible-collections/community.general/pull/10455).

plugins/modules/capabilities.py

@@ -123,6 +123,8 @@ class CapabilitiesModule(object):
             if ' =' in stdout:
                 # process output of an older version of libcap
                 caps = stdout.split(' =')[1].strip().split()
+            elif stdout.strip().endswith(")"):  # '/foo (Error Message)'
+                self.module.fail_json(msg="Unable to get capabilities of %s" % path, stdout=stdout.strip(), stderr=stderr)
             else:
                 # otherwise, we have a newer version here
                 # see original commit message of cap/v0.2.40-18-g177cd41 in libcap.git