On Windows, subprocess.call() fails with an exception if either the executable or any of the arguments contain upper level characters. See below:

>>> cmd = [ u'test_\xc5_exec.bat', u'arg1', u'arg2' ]
>>> subprocess.call(cmd)

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python25\lib\subprocess.py", line 443, in call
    return Popen(*popenargs, **kwargs).wait()
  File "C:\Python25\lib\subprocess.py", line 593, in __init__
    errread, errwrite)
  File "C:\Python25\lib\subprocess.py", line 815, in _execute_child
    startupinfo)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xc5' in position 5: ordinal not in range(128)