fix(test): deregister needs_update bars from global capture registry

test_needs_update starts bars (registering them as global capture
listeners via streams.start_capturing) but never finish()es them, and
one deliberately sets term_width='wide' to prove the width-threshold
math now propagates. That poisoned bar lingered in streams.listeners,
so when a *later* test wrote a newline to the captured stream --
WrappingIO.write calls update() on every listener -- the abandoned bar
hit the int/str division from commit 84b9413 and raised, intermittently
failing test_examples and test_no_newlines (the failure surfaced or hid
depending on freezegun-driven redraw timing).

Add an autouse fixture that deregisters whatever each test started, so
a bar driven into an invalid state can never poison another test.

Author: wolph

tests/test_needs_update.py

@@ -15,6 +15,20 @@
 import pytest
 
 import progressbar
+from progressbar import utils
+
+
+@pytest.fixture(autouse=True)
+def _deregister_started_bars() -> typing.Iterator[None]:
+    # start() registers each bar as a global capture listener (so writes to
+    # the wrapped stream redraw it). These tests deliberately drive bars into
+    # invalid states -- e.g. a non-numeric term_width -- and never finish()
+    # them. Deregister whatever this test started so a poisoned bar cannot be
+    # update()d when a *later* test writes a newline to the captured stream.
+    before = set(utils.streams.listeners)
+    yield
+    for bar in list(utils.streams.listeners - before):
+        utils.streams.stop_capturing(bar)
 
 
 def _bar(**kwargs: typing.Any) -> progressbar.ProgressBar: