Doctest failed with zero exit code

In my test code, my doctest fails but the script exits with a zero return value, which causes the CI run to pass, which is not intended.

Is this the correct behavior of doctest module?

My script ends with:

if __name__ == '__main__':
    import doctest
    doctest.testmod()

The output is like:

**********************************************************************
File "test/test.py", line 7, in __main__
Failed example:
    f(1,0)
Expected:
    -----
    type: <type 'exceptions.ZeroDivisionError'>
    value: integer division or modulo by zero
    x
    -----
Got:
    -----
    type: <type 'exceptions.ZeroDivisionError'>
    value: integer division or modulo by zero
    -----
**********************************************************************
1 items had failures:
   1 of   1 in __main__
***Test Failed*** 1 failures.
tux@iPad:~/programming/exception-notifier(fix-travis)(0)$ echo $?
0

I find using doctest.testmod(raise_on_error=True) will cause an exception to be raised when a test fails, which causes the script exits with a non-zero code.

Python doc here:

Optional argument raise_on_error defaults to false. If true, an exception is raised upon the first failure or unexpected exception in an example. This allows failures to be post-mortem debugged. Default behavior is to continue running examples.