all: Reduce differences with python3.

Using only 2to3 conversions which are python2-compatible.

caucase/ca.py

@@ -625,7 +625,7 @@ class CertificateAuthority(object):
     self._renewCAIfNeeded()
     result = []
     iter_key_pair = iter(self._ca_key_pairs_list)
-    first_key_pair = iter_key_pair.next()
+    first_key_pair = next(iter_key_pair)
     previous_crt_pem = utils.dump_certificate(first_key_pair['crt'])
     previous_key = first_key_pair['key']
     for key_pair in iter_key_pair:

caucase/test.py

@@ -107,7 +107,7 @@ def canConnect(address): # pragma: no cover
   """
   try:
     socket.create_connection(address)
-  except socket.error, e:
+  except socket.error as e:
     if e.errno == errno.ECONNREFUSED:
       return False
     raise
@@ -334,7 +334,7 @@ class CaucaseTest(unittest.TestCase):
           new_key_path,
         ),
       )
-    except SystemExit, e:
+    except SystemExit as e:
       return e.code # pragma: no cover
     except: # pylint: disable=bare-except
       return 1
@@ -896,7 +896,7 @@ class CaucaseTest(unittest.TestCase):
     client = CaucaseClient(self._caucase_url + '/cas')
     try:
       client.createCertificateSigningRequest('Not actually a CSR')
-    except CaucaseError, e:
+    except CaucaseError as e:
       self.assertEqual(e.args[0], 400, e)
     else: # pragma: no cover
       raise AssertionError('Did not raise CaucaseError(400, ...)')

caucase/utils.py

@@ -264,7 +264,7 @@ def _verifyCertificateChain(cert, trusted_cert_list, crl):
   except (
     crypto.X509StoreContextError,
     crypto.Error,
-  ), e:
+  ) as e:
     raise CertificateVerificationError(
       'Certificate verification error: %s' % str(e),
     )

caucase/wsgi.py

@@ -572,13 +572,13 @@ class Application(object):
         raise InsufficientStorage
       except exceptions.NotJSON:
         raise BadRequest('Invalid json payload')
-      except exceptions.CertificateAuthorityException, e:
+      except exceptions.CertificateAuthorityException as e:
         raise BadRequest(str(e))
       except Exception:
         environ['wsgi.errors'].write('Unhandled exception\n')
         traceback.print_exc(file=environ['wsgi.errors'])
         raise ApplicationError
-    except ApplicationError, e:
+    except ApplicationError as e:
       status = e.status
       header_list = e.response_headers
       result = [str(x) for x in e.args]