Revert "missed a line in the test of Issue pandas-dev#3628"

This reverts commit 5b29c68.

Author: stonebig

pandas/io/tests/test_sql.py

@@ -226,8 +226,7 @@ def test_onecolumn_of_integer(self):
         mono_df=DataFrame([1 , 2], columns=['c0'])
         sql.write_frame(mono_df, con = self.db, name = 'mono_df')
         # computing the sum via sql
-        con_x=self.db
-        the_sum=sum([my_c0[0] for  my_c0 in con_x.execute("select * from mono_df")])
+        the_sum=sum([my_c0[0] for  my_c0 in con.execute("select * from mono_df")])
         # it should not fail, and gives 3 ( Issue #3628 )
         self.assertEqual(the_sum , 3)