Restore pytest

Use pytest instead of nosetest

Author: harisbal

pandas/tests/reshape/test_merge.py

@@ -1136,14 +1136,14 @@ def test_join_multi_levels(self):
 
         def f():
             household.join(portfolio, how='inner')
-        self.assertRaises(ValueError, f)
+        pytest.raises(ValueError, f)
 
         portfolio2 = portfolio.copy()
         portfolio2.index.set_names(['household_id', 'foo'])
 
         def f():
             portfolio2.join(portfolio, how='inner')
-        self.assertRaises(ValueError, f)
+        pytest.raises(ValueError, f)
 
     def test_join_multi_levels2(self):
 
@@ -1332,7 +1332,7 @@ def test_join_multi_levels3(self):
 
         def f():
             matrix.join(distances2, how='left')
-        self.assertRaises(TypeError, f)
+        pytest.raises(TypeError, f)
 
         #No-overlapping level names
         distances2 = (
@@ -1348,7 +1348,7 @@ def f():
 
         def f():
             matrix.join(distances2, how='left')
-        self.assertRaises(ValueError, f)
+        pytest.raises(ValueError, f)
 
         # Empty Level
         distances2 = (