Use except x as y instead of except x, y

According to https://docs.python.org/3/howto/pyporting.html the
syntax changed in Python 3.x. The new syntax is usable with
Python >= 2.6 and should be preferred to be compatible with Python3.

Enabled hacking check H231.

Change-Id: Ide60f971493440311f1dcc594e33d536beb925e5

nodepool/nodepool.py

@@ -330,7 +330,7 @@ class NodeLauncher(threading.Thread):
                 dt = self.launchNode(session)
                 failed = False
                 statsd_key = 'ready'
-            except Exception, e:
+            except Exception as e:
                 self.log.exception("%s launching node id: %s "
                                    "in provider: %s error:" %
                                    (e.__class__.__name__,
@@ -571,7 +571,7 @@ class SubNodeLauncher(threading.Thread):
                 dt = self.launchSubNode(session)
                 failed = False
                 statsd_key = 'ready'
-            except Exception, e:
+            except Exception as e:
                 self.log.exception("%s launching subnode id: %s "
                                    "for node id: %s in provider: %s error:" %
                                    (e.__class__.__name__, self.subnode_id,

nodepool/nodeutils.py

@@ -47,11 +47,11 @@ def ssh_connect(ip, username, connect_kwargs={}, timeout=60):
         try:
             client = SSHClient(ip, username, **connect_kwargs)
             break
-        except paramiko.AuthenticationException, e:
+        except paramiko.AuthenticationException as e:
             # This covers the case where the cloud user is created
             # after sshd is up (Fedora for example)
             log.info('Password auth exception. Try number %i...' % count)
-        except socket.error, e:
+        except socket.error as e:
             if e[0] not in [errno.ECONNREFUSED, errno.EHOSTUNREACH]:
                 log.exception('Exception while testing ssh access:')
 

tox.ini

@@ -27,5 +27,6 @@ commands = {posargs}
 
 [flake8]
 ignore = E123,E125,H
+select = H231
 show-source = True
 exclude = .venv,.tox,dist,doc,build,*.egg