Add failing test case for issue 432

[adamchainz]

I've tried to fix it but it seems to be rather tricky and related to a kind of off-by-one error between self.index and output_at that only occurs when there are no blank lines between the encoding comment and the first piece of code in the module.

For #432.

[timothycrosley]

There was some merge issues with this test, but I've copied and pasted it verbatim and added it to my test suite, thanks for providing such a thourough example of the issue to work off of!