gistfile1.txt

rom __future__ import with_statement

from contextlib import contextmanager

import sys

@contextmanager
def open_with_stderr(filename, mode='r'):
    try:
        f = open(filename, mode)
        yield f
    except:
        print >> sys.stderr, "Problems loading from %s" % filename
    else:
        f.close()
        raise

---------------
With this output:
$ python2.5 foo/diskreport.py foo.xml
Problems loading from foo.xml
Traceback (most recent call last):
  File "foo/diskreport.py", line 70, in <module>
    with open_with_stderr(xml_filename, 'r') as xml_file:
  File "/usr/lib/python2.5/contextlib.py", line 17, in __enter__
    raise RuntimeError("generator didn't yield")
RuntimeError: generator didn't yield