fix merge conflict and linting

Author: ryankarlos

pandas/tests/frame/methods/test_asof.py

@@ -1,16 +1,11 @@
+import warnings
+
 import numpy as np
 import pytest
 
 from pandas import DataFrame, Series, Timestamp, date_range, to_datetime
-
 import pandas._testing as tm
 
-import pandas.util.testing as tm
-import warnings
-
-warnings.simplefilter("error")
-
-
 
 @pytest.fixture
 def date_range_frame():