app: use suppress() in simple cases

qubes/app.py

@@ -33,6 +33,7 @@ import tempfile
 import time
 import traceback
 import uuid
+from contextlib import suppress
 
 import asyncio
 import jinja2
@@ -280,11 +281,9 @@ class QubesHost:
 
         self.app.log.debug('QubesHost: no_cpus={} memory_total={}'.format(
             self.no_cpus, self.memory_total))
-        try:
+        with suppress(NotImplementedError):
             self.app.log.debug('QubesHost: xen_free_memory={}'.format(
                 self.get_free_xen_memory()))
-        except NotImplementedError:
-            pass
 
     @property
     def memory_total(self):
@@ -1324,10 +1323,8 @@ class Qubes(qubes.PropertyHolder):
         """
 
         # first search for index, verbatim
-        try:
+        with suppress(KeyError):
             return self.labels[label]
-        except KeyError:
-            pass
 
         # then search for name
         for i in self.labels.values():
@@ -1335,10 +1332,8 @@ class Qubes(qubes.PropertyHolder):
                 return i
 
         # last call, if label is a number represented as str, search in indices
-        try:
+        with suppress(KeyError, ValueError):
             return self.labels[int(label)]
-        except (KeyError, ValueError):
-            pass
 
         raise qubes.exc.QubesLabelNotFoundError(label)
 
@@ -1477,7 +1472,7 @@ class Qubes(qubes.PropertyHolder):
                 # allow removed VM to reference itself
                 continue
             for prop in obj.property_list():
-                try:
+                with suppress(AttributeError):
                     if isinstance(prop, qubes.vm.VMProperty) and \
                             getattr(obj, prop.__name__) == vm:
                         self.log.error(
@@ -1489,8 +1484,6 @@ class Qubes(qubes.PropertyHolder):
                             'see /var/log/qubes/qubes.log in dom0 for '
                             'details'.format(
                                 vm.name))
-                except AttributeError:
-                    pass
 
         assignments = vm.get_provided_assignments()
         if assignments:
@@ -1512,11 +1505,9 @@ class Qubes(qubes.PropertyHolder):
                 'updatevm',
                 'default_template',
         ):
-            try:
+            with suppress(AttributeError):
                 if getattr(self, propname) == vm:
                     delattr(self, propname)
-            except AttributeError:
-                pass
 
     @qubes.events.handler('property-pre-set:clockvm')
     def on_property_pre_set_clockvm(self, event, name, newvalue, oldvalue=None):