lxml >= 5.1.1: SyntaxError: cannot use absolute path on element

[AustinMatherne]

After updating to versions 5.1.1 and 5.2.0, our codebase encounters exceptions when using absolute paths with the iterfind method of an ElementTree object. This behavior deviates from the expected, where a FutureWarning should be logged instead of raising an exception directly.

Expected Behavior:
Absolute paths should trigger a FutureWarning indicating that absolute paths should not be used without interrupting the execution flow.

Actual Behavior:
A SyntaxError exception is raised, which prevents further execution of the script.

Affected Methods:
ElementTree.iterfind raises an exception when used with an absolute path.

Environment tested with:
Python version: 3.12.2
lxml versions: 5.1.1 and 5.2.0

Attachments:
Python script to reproduce the exception.

Steps to Reproduce:
Use the lxml library version 5.1.1 or 5.2.0.
Run the following Python script:

```python
from lxml import etree

xml_string = """
<concept>
    <concept>Content 1</concept>
    <concept>Content 2</concept>
</concept>
"""

root_tree = etree.fromstring(xml_string).getroottree()
root_tree.iterfind("//concept")

```

[scoder (scoder)]

Thanks, that was an update mistake.

Fixed in https://github.com/lxml/lxml/commit/9b8e36d4232aeefc24ce353b33d6b57d750166d3

[scoder (scoder)]

5.1.x branch commit is here:
https://github.com/lxml/lxml/commit/76fd4f944403852f39acfc8a858d0081100e03fe

[scoder (scoder)]

I'll first release this in lxml 5.2.1. The 5.1.2 release doesn't seem urgent, given that this is a) something that users shouldn't do and b) easy to resolve on user side.