[Predicate] Override __bool__ to allow py3 evaluation

The check in `Plugin.test_predicate()` relies on a 'is not None' test,
which on py2 invokes a call to `SoSPredicate.__nonzero__()` which in
turns runs our evaluation of the predicate. On py3 however, this test is
an explicit check to see if the object is `NoneType`. As such,
`__nonzero__()` never runs and the predicate defaults to always
evaluating ad `True`. This effectively removed any gating for command
execution on py3.

By overriding `SoSPredicate.__bool__()` to wrap `__nonzero__()` we can
ensure that predicate evaluation is performed properly on both py2 and
py3 runtimes.

Closes: #1839
Resolves: #1840

Signed-off-by: Jake Hunsaker <jhunsake@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/sos/plugins/__init__.py b/sos/plugins/__init__.py
index ed55ea38..7ed75a5c 100644
--- a/sos/plugins/__init__.py
+++ b/sos/plugins/__init__.py
@@ -203,6 +203,11 @@ class SoSPredicate(object):
         return ((self._eval_kmods() and self._eval_services() and
                  self._eval_packages()) and not self.dry_run)
 
+    def __bool__(self):
+        # Py3 evaluation ends in a __bool__() call where py2 ends in a call
+        # to __nonzero__(). Wrap the latter here, to support both versions
+        return self.__nonzero__()
+
     def __init__(self, owner, dry_run=False, kmods=[], services=[],
                  packages=[], required={}):
         """Initialise a new SoSPredicate object.