Treat pushing a second mouse button during a rectangle zoom as "cancel" rather than putting us in an unresolved state.
Fix so that zooming continues to work even after a box was canceled
Attempt to fix font cache-related test failures
Fix Python 3 unicode issue
Close files opened during testing
Merge pull request #1944 from mdboom/cancel-zoom

ValueError exception in drag_zoom (tk backend)
Merge remote-tracking branch 'upstream/v1.3.x'