See bug 1591774.  

The base problem is that when passing a file:// url into urllib2.urlopen() for a file that doesn't exist, the os.stat() call fails with an OSError exception which is not caught.  The documentation for urllib2 states that urlopen() raises a URLError upon error.

This bug can also be triggered when fetching a http:// url.  A misconfigured webserver can cause urllib2.urlopen to use the FileHandler (see bug report).

This patch catches OSError in the FileHandler class and raises it as a URLError.  Unit test included.

I recall that when I wrote the urllib2 tests there were a fair few cases similar to this -- indeed, this particular one is already marked in the tests with an "XXXX" in test_file().

What do other people think about these -- should they be fixed, or the docs changed?

Sorry, I looked at that commented out section and didn't immediately see what it was for, so ignored it.

I'm not sure what the correct behavior would be in this case.  Getting a OSError from a http:// url is unsettling.

I guess that if I were using the library, I would only want to have to catch one type of exception.  Having to catch both URLError and OSError is inconvenient.  If I were looking for a file on disk I would use file(), so the only time someone probably uses the file:// url syntax is when the end user is entering the URL.  The end user wouldn't distinguish between the two exception types in this case.

I think it should be fixed to raise URLError.

File Added: bug_1591774_failing_test_and_bugfix_v2.patch

Added patch v2 which is a patch against trunk, and adds in the tests that were commented out (they previously failed).

Committed in rev. 54326.

Not backporting since it raises a different exception now.