Do not gather mem facts if command invalid (#40820)

* Do not gather mem facts if command invalid

In some firmwares, 'show memory statistics' fail, thus
do not populate mem if we got a failure after running that command.

* Fix pep8

* Warn if got error when running 'sh memory statistics'

* Fix pep8

(cherry picked from commit 669949e6a3)

lib/ansible/modules/network/ios/ios_facts.py

@@ -228,6 +228,9 @@ class Hardware(FactsBase):
 
         data = self.responses[1]
         if data:
+            if 'Invalid input detected' in data:
+                warnings.append('Unable to gather memory statistics')
+            else:
                 processor_line = [l for l in data.splitlines()
                                   if 'Processor' in l].pop()
                 match = re.findall(r'\s(\d+)\s', processor_line)
@@ -446,6 +449,9 @@ FACT_SUBSETS = dict(
 
 VALID_SUBSETS = frozenset(FACT_SUBSETS.keys())
 
+global warnings
+warnings = list()
+
 
 def main():
     """main entry point for module execution
@@ -508,7 +514,6 @@ def main():
         key = 'ansible_net_%s' % key
         ansible_facts[key] = value
 
-    warnings = list()
     check_args(module, warnings)
 
     module.exit_json(ansible_facts=ansible_facts, warnings=warnings)