Syntax error in example1.py

Run command:
```
examples$ python2 example1.py
```
Output:
```
  File "example1.py", line 76
    sys.exit(app.exec())
                    ^
SyntaxError: invalid syntax
```

Probably the error occurs because `exec` is a keyword in python: https://docs.python.org/2.7/reference/simple_stmts.html#exec

Python 2.7.13