py3: wrap tempfile.NamedTemporaryFile() to return bytes fp.name
Unlike its name, tempfile.NamedTemporaryFile is not a class, so I renamed
the pycompat version to look like a plain function.
Since temp.name uses in the infinitepush extension aren't bytes-safe, this
patch leaves them unmodified. Another weird thing is tempfile.mktemp(),
which does not accept bytes suffix nor prefix. Sigh.
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