Resume after exception

[peterbe at gmail.com]

Why does the first function return True? Shouldn't it return the file
content? That's at least what the function name implies.
You call the second function open_command() which returns a boolean.
Feels wrong.

Where you have written "How?" I suggest that you replace that by:
return open_file("foo.bar", 1)

and change open_file() to look something like this:
 def open_file(file_name, ignore_lock=False):
    f = file(file_name, 'r')
    {read first line for file lock info}
    if first_line == "FILE LOCKED" and not ignore_lock:
        raise FileLockedException(lock_user, lock_timestamp)
    {read remainder of file}
    return True