We silently dropped all integer values to install_mode since the
original implementation of doing this in KwargInfo, in commit
596c8d4af5.
This happened because install_mode is supposed to convert False
(exactly) to None, and otherwise pass all arguments in place. But a
generator is homogeneous and attempting to do this correctly produced a
mypy error that FileMode arguments were allowed to be ints -- well of
course they are -- so that resulted in the convertor... treating ints
like False instead, to make mypy happy.
Fixes#11538