gh-145259: Fix xml.dom.pulldom dropping events produced by parser.close()

[zetzschest]

Issue

When the input stream is exhausted, getEvent() calls self.parser.close() and immediately returns None without checking whether close() generated new events. SAX events emitted during close() (e.g. END_ELEMENT for the final tag) are silently lost.

Reproducer

import io
from xml.dom.pulldom import parse
events = list(parse(io.BytesIO(b'<a></a>'), bufsize=2))
print([e for e, _ in events])  # ['START_DOCUMENT', 'START_ELEMENT'] — END_ELEMENT missing

Fix

In Lib/xml/dom/pulldom.py, after calling self.parser.close(), check if new events were produced before returning None:

self.parser.close()
if self.pulldom.firstEvent[1]:
    break
return None

Test updates

Two existing tests in test_pulldom needed adjustments since they were based on the previous behavior:

• test_end_document was marked @expectedFailure — it now passes as the END_DOCUMENT event is correctly delivered.
• test_expandItem expected StopIteration immediately after </html> — updated to account for the additional events (like END_DOCUMENT) that are now properly emitted.

• Issue: xml.dom.pulldom DOMEventStream drops SAX events produced by parser.close() #145259

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