AIX

#!/usr/bin/python
import hashlib

<project name="ant_test" default="python">
        <target name="python" >
                <exec executable="./test.py" failifexecutionfails="true" failonerror="true"/>
        </target>
</project>

$ ls -l
total 16
-rw-r--r--    1 dhs      usr             170 Dec 20 15:46 ant_test.xml
-rwxr-xr-x    1 dhs      usr              35 Dec 20 09:54 test.py
$ ./test.py
$ echo $?
0
$ ant -f ant_test.xml
Buildfile: /home/RECOMMIND/dhs/tmp/ant_test.xml

python:
     [exec] Traceback (most recent call last):
     [exec]   File "./test.py", line 3, in <module>
     [exec]     import hashlib
     [exec]   File "/opt/freeware/lib/python2.6/hashlib.py", line 136, in <module>
     [exec]     md5 = __get_builtin_constructor('md5')
     [exec]   File "/opt/freeware/lib/python2.6/hashlib.py", line 63, in __get_builtin_constructor
     [exec]     import _md5
     [exec] ImportError: No module named _md5

BUILD FAILED
/home/RECOMMIND/dhs/tmp/ant_test.xml:3: exec returned: 1

Total time: 1 second