Use Python 3.x compatible except construct

Python 3.x deprecated excecpt x,y. Use except x as y,
which works with any Python version >= 2.6

Change-Id: I264049ee41e75bcedea86adf7c2011c343f47ddb

bin/heat-api

@@ -61,5 +61,5 @@ if __name__ == '__main__':
         server = wsgi.Server()
         server.start(app, cfg.CONF, default_port=port)
         server.wait()
-    except RuntimeError, e:
+    except RuntimeError as e:
         sys.exit("ERROR: %s" % e)

bin/heat-api-cfn

@@ -63,5 +63,5 @@ if __name__ == '__main__':
         server = wsgi.Server()
         server.start(app, cfg.CONF, default_port=port)
         server.wait()
-    except RuntimeError, e:
+    except RuntimeError as e:
         sys.exit("ERROR: %s" % e)

bin/heat-cfn

@@ -682,7 +682,7 @@ Commands:
         sys.exit(result)
     except (RuntimeError,
             NotImplementedError,
-            exception.ClientConfigurationError), ex:
+            exception.ClientConfigurationError) as ex:
         oparser.print_usage()
         logging.error("ERROR: %s" % ex)
         sys.exit(1)

bin/heat-watch

@@ -270,7 +270,7 @@ Commands:
         sys.exit(result)
     except (RuntimeError,
             NotImplementedError,
-            exception.ClientConfigurationError), ex:
+            exception.ClientConfigurationError) as ex:
         oparser.print_usage()
         logging.error("ERROR: %s" % ex)
         sys.exit(1)