instantiateVariableFont with default inplace=False returns a *new*
TTFont; rebinding `font` strands the source TTFont and its file handle
open until GC. The trailing font.close() then closes only the new
pinned-instance object.
Capture the source as a separate reference and close both with nested
try/finally: inner finally closes the static instance after save (or
on save failure), outer finally closes the source unconditionally.
jpirnay
ad52abf069