Fixed formatting. Added comment with issue number to test.

Author: Joshua Bradt

doc/source/whatsnew/v0.20.0.txt

@@ -517,4 +517,4 @@ Bug Fixes
 
 - Bug in ``DataFrame.boxplot`` where ``fontsize`` was not applied to the tick labels on both axes (:issue:`15108`)
 - Bug in ``Series.replace`` and ``DataFrame.replace`` which failed on empty replacement dicts (:issue:`15289`)
-- Bug in ``pd.melt`` where passing a tuple value for ``value_vars`` caused a TypeError (:issue:`15348`)
+- Bug in ``pd.melt`` where passing a tuple value for ``value_vars`` caused a ``TypeError`` (:issue:`15348`)

pandas/tests/test_reshape.py

@@ -57,6 +57,7 @@ def test_value_vars(self):
         tm.assert_frame_equal(result4, expected4)
 
     def test_value_vars_types(self):
+        # GH 15348
         expected = DataFrame({'id1': self.df['id1'].tolist() * 2,
                               'id2': self.df['id2'].tolist() * 2,
                               'variable': ['A'] * 10 + ['B'] * 10,