Apply suggestions from code review

Co-authored-by: Eric Larson <[email protected]>

mne/tests/test_epochs.py

@@ -488,11 +488,10 @@ def test_average_movements():
 
 def _assert_drop_log_types(drop_log):
     __tracebackhide__ = True
-    assert isinstance(drop_log, tuple), """drop_log should be tuple
-    or list"""
+    assert isinstance(drop_log, tuple), "drop_log should be tuple"
     assert all(
         isinstance(log, tuple) for log in drop_log
-    ), "drop_log[ii] should be tuple or list"
+    ), "drop_log[ii] should be tuple"
     assert all(
         isinstance(s, str) for log in drop_log for s in log
     ), "drop_log[ii][jj] should be str"