Improve Python 3.x compatibility

Mechanical translation of the deprecated
except x,y: construct with except x as y:
The latter works with any Python >= 2.6.
Add Hacking check.

Change-Id: I845829d97d379c1cd9b3a77e7e5786586f263b64

HACKING.rst

@@ -211,6 +211,25 @@ Example::
     LOG.error(msg % {"s_id": "1234", "m_key": "imageId"})
 
 
+Python 3.x compatibility
+------------------------
+Nova code should stay Python 3.x compatible. That means all Python 2.x-only
+constructs should be avoided. An example is
+
+    except x,y:
+
+Use
+
+    except x as y:
+
+instead. Other Python 3.x compatility issues, like e.g. print operator
+can be avoided in new code by using
+
+    from __future__ import print_function
+
+at the top of your module.
+
+
 Creating Unit Tests
 -------------------
 For every new feature, unit tests should be created that both test and

nova/exception.py

@@ -73,7 +73,7 @@ def wrap_exception(notifier=None, publisher_id=None, event_type=None,
             # contain confidential information.
             try:
                 return f(self, context, *args, **kw)
-            except Exception, e:
+            except Exception as e:
                 with excutils.save_and_reraise_exception():
                     if notifier:
                         payload = dict(exception=e)

nova/openstack/common/processutils.py

@@ -203,7 +203,7 @@ def trycmd(*args, **kwargs):
     try:
         out, err = execute(*args, **kwargs)
         failed = False
-    except ProcessExecutionError, exn:
+    except ProcessExecutionError as exn:
         out, err = '', str(exn)
         failed = True
 

nova/scheduler/scheduler_options.py

@@ -66,7 +66,7 @@ class SchedulerOptions(object):
         """Get the last modified datetime. Broken out for testing."""
         try:
             return os.path.getmtime(filename)
-        except os.error, e:
+        except os.error as e:
             with excutils.save_and_reraise_exception():
                 LOG.exception(_("Could not stat scheduler options file "
                                 "%(filename)s: '%(e)s'"), locals())
@@ -75,7 +75,7 @@ class SchedulerOptions(object):
         """Decode the JSON file. Broken out for testing."""
         try:
             return json.load(handle)
-        except ValueError, e:
+        except ValueError as e:
             LOG.exception(_("Could not decode scheduler options: "
                             "'%(e)s'") % locals())
             return {}

nova/tests/test_api.py

@@ -309,7 +309,7 @@ class ApiEc2TestCase(test.TestCase):
 
         try:
             self.ec2.create_key_pair('test')
-        except boto_exc.EC2ResponseError, e:
+        except boto_exc.EC2ResponseError as e:
             if e.code == 'InvalidKeyPair.Duplicate':
                 pass
             else:

nova/tests/test_migrations.py

@@ -219,7 +219,7 @@ class BaseMigrationTestCase(test.TestCase):
                 for key, value in defaults.items():
                     self.test_databases[key] = value
                 self.snake_walk = cp.getboolean('walk_style', 'snake_walk')
-            except ConfigParser.ParsingError, e:
+            except ConfigParser.ParsingError as e:
                 self.fail("Failed to read test_migrations.conf config "
                           "file. Got error: %s" % e)
         else:

nova/utils.py

@@ -927,7 +927,7 @@ def tempdir(**kwargs):
     finally:
         try:
             shutil.rmtree(tmpdir)
-        except OSError, e:
+        except OSError as e:
             LOG.error(_('Could not remove tmpdir: %s'), str(e))
 
 
@@ -1007,7 +1007,7 @@ def last_bytes(file_like_object, num):
 
     try:
         file_like_object.seek(-num, os.SEEK_END)
-    except IOError, e:
+    except IOError as e:
         if e.errno == 22:
             file_like_object.seek(0, os.SEEK_SET)
         else:
@@ -1074,7 +1074,7 @@ class ExceptionHelper(object):
         def wrapper(*args, **kwargs):
             try:
                 return func(*args, **kwargs)
-            except rpc_common.ClientException, e:
+            except rpc_common.ClientException as e:
                 raise (e._exc_info[1], None, e._exc_info[2])
         return wrapper