This is a regression in lxml 5.2.0/5.2.1: it hands parsel a bytes object where a string encoding name belongs, and Python's codec lookup chokes on the repr. Upgrade or downgrade lxml out of the broken range (`python -m pip install -U lxml` once a fixed release is out, or pin `lxml==5.1.0`) and the LookupError disappears.

## The error

```text
LookupError: unknown encoding: 'b'utf8''
```

## Fix it

1. **Check your lxml version**

```
python -c "import lxml.etree; print(lxml.etree.LXML_VERSION)"
```
Expected: if it prints `(5, 2, 0, 0)` or `(5, 2, 1, 0)`, you have the broken build.

2. **Move lxml out of the broken range**

```
python -m pip install -U lxml
```
Expected: installs 5.2.2 or newer, where the regression is fixed. If you must stay pinned, `python -m pip install lxml==5.1.0` also avoids it.

3. **Confirm the selector works**

```
python -c "from parsel import Selector; print(Selector('hi').xpath('string()').get())"
```
Expected: prints `hi` with no LookupError.

## When this applies

- the LookupError names the encoding `'b'utf8''` (note the doubled quotes, it is a bytes repr)
- it comes from `parsel.Selector(...)` or Scrapy's `TextResponse`
- it started right after an lxml upgrade to 5.2.x

## When it does NOT apply

- `LookupError: unknown encoding: 'utf8'` (no b-prefix) is a genuinely misspelled encoding somewhere in your code
- import errors for lxml itself are the missing/broken lxml problem

## Compatibility

Broken: lxml 5.2.0 and 5.2.1. Fixed: lxml 5.2.2+. parsel versions are all affected equally because the bug is underneath parsel in lxml.

## Why it happens

lxml 5.2 changed how it reports the document encoding to callers, and in two releases it returned the raw bytes `b'utf8'` instead of the string `'utf8'`. parsel passes that value to Python's codec machinery, which stringifies the bytes object into the nonsense name `'b'utf8''` and raises LookupError. Nothing is wrong with your HTML or your code.

## Edge cases

- If your lockfile pins lxml==5.2.1, bump the pin. The regression is in lxml, not parsel, so upgrading parsel alone does nothing.
- Scrapy users hit this through `TextResponse`; the fix is the same lxml move, not a Scrapy upgrade.
- If you cannot touch lxml (vendored env), decoding the body yourself and passing `text=` instead of `body=` sidesteps the encoding detection path.