When doing the quick test to see whether large files are supported,

catch IOError as well as OverflowError.  I found that on Tru64 Unix
this was raised; probably because the OS (or libc) doesn't support
large files but the architecture is 64 bits!

Lib/test/test_largefile.py

@@ -16,7 +16,7 @@ f = open(test_support.TESTFN, 'w')
 try:
     # 2**31 == 2147483648
     f.seek(2147483649L)
-except OverflowError:
+except (IOError, OverflowError):
     f.close()
     os.unlink(test_support.TESTFN)
     raise test_support.TestSkipped, \