fix pep8

Author: charlesdong1991

pandas/tests/reshape/merge/test_merge.py

@@ -22,7 +22,7 @@
 from pandas.core.reshape.concat import concat
 from pandas.core.reshape.merge import MergeError, merge
 import pandas.util.testing as tm
-from pandas.util.testing import assert_frame_equal, assert_series_equal, assert_index_equal
+from pandas.util.testing import assert_frame_equal, assert_series_equal
 
 N = 50
 NGROUPS = 8
@@ -1454,8 +1454,8 @@ def test_merge_suffix(col1, col2, suffixes, expected_cols):
     a = pd.DataFrame({col1: [1, 2, 3]})
     b = pd.DataFrame({col2: [4, 5, 6]})
 
-    suffix_df = a.merge(b, left_index=True, right_index=True, suffixes=suffixes)
-    assert suffix_df.columns.tolist() == expected_cols
+    df = a.merge(b, left_index=True, right_index=True, suffixes=suffixes)
+    assert df.columns.tolist() == expected_cols
 
     with pytest.raises(ValueError):
         a.merge(b, left_index=True, right_index=True, suffixes=(None, None))