Test failure pandas.tests.io.test_sql.TestXSQLite
I'm seeing a test failure locally on master (83436af8ae1ccad49b7ceac7471c060d823d10ab) that doesn't appear to be reflected in the CI.

Strangely, `python -m pytest pandas/tests/io/test_sql.py` goes through just fine.  It gets triggered when I run:

```
>>> import matplotlib        # import order matters here
>>> matplotlib.use('Agg')  # needed to avoid matplotlib errors on a headless machine
>>> import pandas as pd
>>> pd.test()
[...]
___________________________________________________________________ TestXSQLite.test_write_row_by_row ____________________________________________________________________

self = <pandas.tests.io.test_sql.TestXSQLite object at 0x7f99def27850>

    def test_write_row_by_row(self):
    
        frame = tm.makeTimeDataFrame()
        frame.iloc[0, 0] = np.nan
        create_sql = sql.get_schema(frame, 'test')
        cur = self.conn.cursor()
        cur.execute(create_sql)
    
        cur = self.conn.cursor()
    
        ins = "INSERT INTO test VALUES (%s, %s, %s, %s)"
        for idx, row in frame.iterrows():
            fmt_sql = format_query(ins, *row)
            tquery(fmt_sql, cur=cur)
    
        self.conn.commit()
    
        result = sql.read_sql("select * from test", con=self.conn)
        result.index = frame.index
>       tm.assert_frame_equal(result, frame)

pandas/tests/io/test_sql.py:2134: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
pandas/util/testing.py:1402: in assert_frame_equal
    obj='DataFrame.iloc[:, {idx}]'.format(idx=i))
pandas/util/testing.py:1281: in assert_series_equal
    obj='{obj}'.format(obj=obj))
pandas/_libs/testing.pyx:59: in pandas._libs.testing.assert_almost_equal
    cpdef assert_almost_equal(a, b,
pandas/_libs/testing.pyx:173: in pandas._libs.testing.assert_almost_equal
    raise_assert_detail(obj, msg, lobj, robj)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

obj = 'DataFrame.iloc[:, 2]', message = 'DataFrame.iloc[:, 2] values are different (1.0 %)'
left = '[-0.59787048, 1.75727252, -0.1310937, -0.24085753, -1.55551175, 1.56304803, 0.43139791, 0.65542659, 0.0821268, -2.194...3087, 1.24262929, 0.25190051, -0.07253108, -0.8719974, -0.68566296, 0.00038078, -0.15632703, -0.46625691, -0.01641763]'
right = '[-0.597870480786, 1.75727252312, -0.131093699304, -0.240857530072, -1.55551175168, 1.56304803297, 0.431397907647, 0.6...725310846663, -0.871997401837, -0.685662960253, 0.000380776752185, -0.156327025786, -0.466256909406, -0.0164176348789]'
diff = None

    def raise_assert_detail(obj, message, left, right, diff=None):
        if isinstance(left, np.ndarray):
            left = pprint_thing(left)
        if isinstance(right, np.ndarray):
            right = pprint_thing(right)
    
        msg = """{obj} are different
    
    {message}
    [left]:  {left}
    [right]: {right}""".format(obj=obj, message=message, left=left, right=right)
    
        if diff is not None:
            msg += "\n[diff]: {diff}".format(diff=diff)
    
>       raise AssertionError(msg)
E       AssertionError: DataFrame.iloc[:, 2] are different
E       
E       DataFrame.iloc[:, 2] values are different (1.0 %)
E       [left]:  [-0.59787048, 1.75727252, -0.1310937, -0.24085753, -1.55551175, 1.56304803, 0.43139791, 0.65542659, 0.0821268, -2.19483669, 1.29691261, 0.86777117, 0.36392125, -0.57871272, 1.51058845, 1.09966946, -0.55036466, -0.40261691, -0.08746403, -0.45147578, 1.41894647, -0.4797129, 0.37331928, 0.26579615, -0.83709729, 0.31505209, -0.92100097, 0.10158214, -0.53096049, 0.06649923, -2.00748014, 2.22979451, 0.08193706, 0.14799922, 0.17588662, 0.86689148, -1.09017582, -1.81591557, 0.54031046, -0.11075987, 1.01837036, 1.98109779, -0.4993707, -1.59367359, -2.08201023, 0.88399937, 1.24248965, -0.37544702, -0.48737033, -1.3391138, -2.8575393, 0.89456229, -0.05170464, 1.13538934, 1.01720956, 0.16289824, -0.37986802, -0.89600403, -0.20111217, -0.05674187, 0.21197277, 0.62103332, -0.17917755, 0.88623787, 0.89353538, 0.89794712, -0.81026691, 0.04248671, -0.62944966, -1.07986145, -0.21194148, 0.71853091, 0.82763943, -1.53930274, 0.79953673, 0.65268344, 0.38126291, 1.68621206, -0.58234383, 0.53573623, -1.87181172, 1.81584145, 0.01156531, 1.00901096, -0.04814026, -0.06214, 0.55437294, -0.05109543, -0.40641954, -0.56006971, -0.14203087, 1.24262929, 0.25190051, -0.07253108, -0.8719974, -0.68566296, 0.00038078, -0.15632703, -0.46625691, -0.01641763]
E       [right]: [-0.597870480786, 1.75727252312, -0.131093699304, -0.240857530072, -1.55551175168, 1.56304803297, 0.431397907647, 0.655426586864, 0.0821268019634, -2.19483669218, 1.29691260774, 0.867771165078, 0.363921245537, -0.578712721937, 1.5105884463, 1.09966945821, -0.550364664379, -0.402616908529, -0.0874640312425, -0.451475782528, 1.41894646672, -0.479712901824, 0.373319283832, 0.265796151564, -0.837097285667, 0.315052093362, -0.921000967868, 0.101582144906, -0.530960487754, 0.0664992299507, -2.00748013934, 2.22979451164, 0.0819370606265, 0.147999223147, 0.175886617188, 0.866891479712, -1.09017582435, -1.81591556915, 0.540310455382, -0.110759871621, 1.01837036341, 1.98109778942, -0.499370703418, -1.59367359033, -2.08201023199, 0.883999370748, 1.24248965221, -0.375447016032, -0.487370326597, -1.3391138024, -2.85753930098, 0.894562293166, -0.0517046435105, 1.13538933705, 1.01720956219, 0.162898242598, -0.379868021698, -0.896004027455, -0.201112174114, -0.056741869755, 0.211972767677, 0.621033324798, -0.179177554443, 0.886237870665, 0.89353538222, 0.897947121995, -0.810266911765, 0.0424867143869, -0.6294496634, -1.0798614477, -0.211941482626, 0.718530908141, 0.82763942996, -1.53930273634, 0.799536732242, 0.65268344093, 0.381262905684, 1.68621205795, -0.582343833696, 0.535736231547, -1.87181171881, 1.81584145215, 0.0115653145115, 1.00901096046, -0.0481402575178, -0.0621399986677, 0.554372937832, -0.0510954278629, -0.406419542776, -0.560069714991, -0.142030873399, 1.24262929489, 0.251900511488, -0.0725310846663, -0.871997401837, -0.685662960253, 0.000380776752185, -0.156327025786, -0.466256909406, -0.0164176348789]

pandas/util/testing.py:1105: AssertionError
```

Py2.7.12, Ubuntu 16.04