Correctly raise ValueError on unknown binding in KeyBindings.remove() #2042
Description
When trying to remove from KeyBindings by Keys, an undocumented UnboundLocalError exception is raised instead of the documented ValueError.
To repro can add something like the following to test_remove_bindings:
h3 = handlers.controla
...
# Test passing unbound key sequence to the remove() function
with pytest.raises(ValueError):
bindings.remove(h3)
with pytest.raises(ValueError):
bindings.remove(Keys.ControlA)