I think the following error output unsatisfactory as it does not give me
any hint what file was not found:

$ fetch_quals.py blah.txt 
Traceback (most recent call last):
  File "/home/mmokrejs/bin/fetch_quals.py", line 15, in <module>
    _p1 = subprocess.Popen(['query_tracedb', 'retrieve', 'quality',
_id], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
  File "/usr/lib/python2.5/subprocess.py", line 594, in __init__
    errread, errwrite)
  File "/usr/lib/python2.5/subprocess.py", line 1091, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
$

I know now that I had to specify full path tot he binary or include
shell=True argument but anyway, please improve the error message.