Migrate from `pkg_resources` to `importlib.metadata` in `tests/test_plugin.py`

[juliangilbey]

According to https://setuptools.pypa.io/en/latest/pkg_resources.html, pkg_resources is deprecated in favour of importlib.metadata. Unfortunately, though, the semantics of the entry_points() function changed in Python 3.10. So once support for Pythons 3.8 and 3.9 is dropped in python-lsp-black, this could be migrated to the preferred importlib.metadata tools. (One could have a conditional for Python >= 3.10 in the meantime, but that would be ugly.)

Here is a patch that should work on Python 3.10+:

--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -2,10 +2,10 @@
 import types
 from pathlib import Path
 from unittest.mock import Mock
+from importlib.metadata import entry_points
 
 # Third-party imports
 import black
-import pkg_resources
 import pytest
 
 # Python LSP imports
@@ -321,8 +321,7 @@
 
 
 def test_entry_point():
-    distribution = pkg_resources.get_distribution("python-lsp-black")
-    entry_point = distribution.get_entry_info("pylsp", "black")
+    (entry_point,) = entry_points(group="pylsp", name="black")
 
     assert entry_point is not None