Skip autobpm tests if librosa isn't available

Except under GitHub CI, where we expect all tests to run.

Author: stefanor

test/plugins/test_autobpm.py

@@ -1,7 +1,14 @@
+import importlib.util
+import os
+
 import pytest
 
 from beets.test.helper import ImportHelper, PluginMixin
 
+github_ci = os.environ.get("GITHUB_ACTIONS") == "true"
+if not github_ci and not importlib.util.find_spec("librosa"):
+    pytest.skip("librosa isn't available", allow_module_level=True)
+
 
 class TestAutoBPMPlugin(PluginMixin, ImportHelper):
     plugin = "autobpm"