[In Go, strings can contain arbitrary bytes](https://go.dev/blog/strings)
(similar to the ones in Python 2), and there is no explicit `bytes`
class.
Thus, all the code that deals with arbitrary data in Go is currently
using the string type.

However, the [ogórek package](https://github.com/kisielk/og-rek) used
to load Python pickles in Go, decodes Python 3 `bytes` objects as a
special string type `ogórek.Bytes`, incompatible with APIs expecting
normal strings.
This causes errors such as the following:
```
--- FAIL: TestΔFtail (1.31s)
panic: @03f97a3b982b7bcc: get blkdata from obj 0000000000000002: ZBlk0(0000000000000002): loadBlkData: wendelin.bigfile.file_zodb.ZBlk0(0000000000000002): activate: pysetstate: expect str; got ogórek.Bytes [recovered]
        panic: file:///tmp/TestΔFtail493253177/001/1.fs: @03f97a3b982b7bcc: get blktab: @03f97a3b982b7bcc: get blkdata from obj 0000000000000002: ZBlk0(0000000000000002): loadBlkData: wendelin.bigfile.file_zodb.ZBlk0(0000000000000002): activate: pysetstate: expect str; got ogórek.Bytes [recovered]
        panic: file:///tmp/TestΔFtail493253177/001/1.fs: @03f97a3b982b7bcc: get blktab: @03f97a3b982b7bcc: get blkdata from obj 0000000000000002: ZBlk0(0000000000000002): loadBlkData: wendelin.bigfile.file_zodb.ZBlk0(0000000000000002): activate: pysetstate: expect str; got ogórek.Bytes
```

In order to fix that, we have copied the [`Xstrbytes` function from NEO](
https://lab.nexedi.com/kirr/neo/-/blob/f7776fc1689b0d62e582b132ecc017ab72dc3b23/go/zodb/internal/pickletools/pickletools.go#L49-64)
in the `pycompat.go` file, which accepts either a string or an
`ogórek.Bytes` object and returns the corresponding string.

We have used that function whenever a `bytes` object could be present.