Flush count overflow issue mitigation

[ghoober]

Hopefully this can save users some effort. Needs more testing.

[ghoober]

I moved the exception to the end of the flush function so that the current work will still be flushed. Will update the PR after testing.

[ghoober]

Cleaned up a bit. Finally the last flush should work, too.

I am thinking about adding a sys.exit(8) code so that it is easier to deal with the error from shell. Or maybe writing the flush count to a file. @SomberNight let me know if that sounds interesting at all.