Do not skip tests in ci.

The return type of the stage decorator should in theory be `T|None`
but the return of task types is not consistent in its usage. Would need
some bigger changes for which I'm not ready at the moment.

beets/util/pipeline.py

@@ -160,7 +160,7 @@ R = TypeVar("R")
 def stage(
     func: Callable[
         [Unpack[A], T],
-        R,
+        Optional[R],
     ],
 ):
     """Decorate a function to become a simple stage.
@@ -176,7 +176,7 @@ def stage(
     [3, 4, 5]
     """
 
-    def coro(*args: Unpack[A]) -> Generator[Union[R, T, None], T, None]:
+    def coro(*args: Unpack[A]) -> Generator[Union[R, T, None], T, R]:
         task = None
         while True:
             task = yield task
@@ -185,7 +185,7 @@ def stage(
     return coro
 
 
-def mutator_stage(func: Callable[[Unpack[A], T], None]):
+def mutator_stage(func: Callable[[Unpack[A], T], R]):
     """Decorate a function that manipulates items in a coroutine to
     become a simple stage.
 
@@ -200,7 +200,7 @@ def mutator_stage(func: Callable[[Unpack[A], T], None]):
     [{'x': True}, {'a': False, 'x': True}]
     """
 
-    def coro(*args: Unpack[A]) -> Generator[Optional[T], T, None]:
+    def coro(*args: Unpack[A]) -> Generator[Union[T, None], T, None]:
         task = None
         while True:
             task = yield task

test/plugins/test_lyrics.py

@@ -14,6 +14,8 @@
 
 """Tests for the 'lyrics' plugin."""
 
+import importlib.util
+import os
 import re
 from functools import partial
 from http import HTTPStatus
@@ -22,15 +24,15 @@ import pytest
 
 from beets.library import Item
 from beets.test.helper import PluginMixin
-
-try:
-    from beetsplug import lyrics
-except Exception:
-    pytest.skip("lyrics plugin couldn't be loaded", allow_module_level=True)
-
+from beetsplug import lyrics
 
 from .lyrics_pages import LyricsPage, lyrics_pages
 
+github_ci = os.environ.get("GITHUB_ACTIONS") == "true"
+if not github_ci and not importlib.util.find_spec("langdetect"):
+    pytest.skip("langdetect isn't available", allow_module_level=True)
+
+
 PHRASE_BY_TITLE = {
     "Lady Madonna": "friday night arrives without a suitcase",
     "Jazz'n'blues": "as i check my balance i kiss the screen",