_Binder.visit_Global marked the name ambiguous in the module, so `global execute` in a
function hid `from subprocess import run as execute` and HX006 (missing timeout) never
fired on `execute(cmd)`; nonlocal did the same for an enclosing function's import. A
declaration selects the outer binding, it does not rebind it: declared names now resolve
in the scope they point at, and only an assignment (or import) through the declaration
rebinds that outer name.
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