Original patch by Vinay Sajip on #11637.

Andrew agreed in the issue that eliminating the module file made sense.
Wrapper has only been exposed as a function, and so there is no (easy)
way to access the wrapper module, which in any case only had the one
function in it.  Since __init__ already contains a couple wrapper
functions, it seems to make sense to just move wrapper there instead of
importing it from a single function module.

Patch by July Tikhonov.

Analogous to the decode_header fix, this fix makes Header.append and
make_header correctly handle the unknown-8bit charset introduced by email5.1,
when the input to them is binary strings.  Previous to this fix the
make_header(decode_header(x)) == x invariant was broken in the face of the
unknown-8bit charset.

This updates 12e39cd7a0e4 (merge of b21fdfa0019c), which fixed this bug
incorrectly.

This updates b21fdfa0019c, which fixed this bug incorrectly.

This makes them work like the close provided by regular file objects.

All of the other methods in mailbox that create message objects take care to
close the file descriptors they use, so it seems to make sense to have
__getitem__ do so as well.

Patch by Filip Gruszczyński.

- Move a tearDown method right after setUp
- Use assertRaises instead of reinventing it
- Skip a test instead of commenting it out, as a reminder

Victor Stinner diagnosed on #12167 that some reference leaks came from
util._path_created, a set used for caching; there are two tests that
cause additions to this set, so now they clear it in tearDown, avoiding
17 refleaks.  (My tests show that it’s necessary to clear the set in
only one test, clearing it in both does not stop more refleaks, but
there’s no harm in doing it.)

Fix os.fchown() and os.open()

Remove also trailing spaces and replace tabs by spaces.