Tomasz Sokolowski

This issue affects `SinglePartWriter` as well. The problem boils down to how garbage collection of both `SinglepartWriter` and `MultipartWriter` is being done. Both writers inherit from `io.BufferedIOBase` which calls `self.close()`...

@ddelange regardless of patches for `TextIOWrapper` implemented in `v7.0.0` `close()` will be called on both writers when garbage collected, resulting in unwanted writes to S3.

@mpenkov After doing some more troubleshooting I've created separate issue #819 as the problem I've mentioned affects only `SinglepartWriter` at the moment. Fix for that is quite simple and I...

@ddelange This is exactly what the fix should be, as I mentioned in #763. I will PR it in few moments.