diff --git a/ci/requirements-3.6.build b/ci/requirements-3.6.build
index 1c4b46aea3865..94e1152450d87 100644
--- a/ci/requirements-3.6.build
+++ b/ci/requirements-3.6.build
@@ -2,5 +2,5 @@ python=3.6*
 python-dateutil
 pytz
 nomkl
-numpy
+numpy=1.13.*
 cython
diff --git a/pandas/core/base.py b/pandas/core/base.py
index 280b8849792e3..fb93fde6d3a21 100644
--- a/pandas/core/base.py
+++ b/pandas/core/base.py
@@ -46,7 +46,7 @@ class StringMixin(object):
     # Formatting
 
     def __unicode__(self):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     def __str__(self):
         """
@@ -278,10 +278,10 @@ def _gotitem(self, key, ndim, subset=None):
             subset to act on
 
         """
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     def aggregate(self, func, *args, **kwargs):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     agg = aggregate
 
@@ -1247,4 +1247,4 @@ def duplicated(self, keep='first'):
     # abstracts
 
     def _update_inplace(self, result, **kwargs):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
diff --git a/pandas/core/resample.py b/pandas/core/resample.py
index 772568ee84737..af747ac4d3b20 100644
--- a/pandas/core/resample.py
+++ b/pandas/core/resample.py
@@ -233,7 +233,7 @@ def _convert_obj(self, obj):
         return obj
 
     def _get_binner_for_time(self):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     def _set_binner(self):
         """
@@ -372,10 +372,10 @@ def transform(self, arg, *args, **kwargs):
             arg, *args, **kwargs)
 
     def _downsample(self, f):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     def _upsample(self, f, limit=None, fill_value=None):
-        raise AbstractMethodError(self)
+        raise com.AbstractMethodError(self)
 
     def _gotitem(self, key, ndim, subset=None):
         """
diff --git a/pandas/tests/frame/test_operators.py b/pandas/tests/frame/test_operators.py
index 5df50f3d7835b..3a146cbf7c438 100644
--- a/pandas/tests/frame/test_operators.py
+++ b/pandas/tests/frame/test_operators.py
@@ -28,6 +28,53 @@
                                        _check_mixed_int)
 
 
+class TestDataFrameArithmetic(object):
+
+    @pytest.mark.xfail(reason='GH#7996 datetime64 units not converted to nano')
+    def test_frame_sub_datetime64_not_ns(self):
+        df = pd.DataFrame(date_range('20130101', periods=3))
+        dt64 = np.datetime64('2013-01-01')
+        assert dt64.dtype == 'datetime64[D]'
+        res = df - dt64
+        expected = pd.DataFrame([pd.Timedelta(days=0), pd.Timedelta(days=1),
+                                 pd.Timedelta(days=2)])
+        tm.assert_frame_equal(res, expected)
+
+    @pytest.mark.parametrize('data', [
+        [1, 2, 3],
+        [1.1, 2.2, 3.3],
+        [pd.Timestamp('2011-01-01'), pd.Timestamp('2011-01-02'), pd.NaT],
+        ['x', 'y', 1]])
+    @pytest.mark.parametrize('dtype', [None, object])
+    def test_frame_radd_str_invalid(self, dtype, data):
+        df = DataFrame(data, dtype=dtype)
+        with pytest.raises(TypeError):
+            'foo_' + df
+
+    @pytest.mark.parametrize('dtype', [None, object])
+    def test_frame_with_dtype_radd_int(self, dtype):
+        df = pd.DataFrame([1, 2, 3], dtype=dtype)
+        expected = pd.DataFrame([2, 3, 4], dtype=dtype)
+        result = 1 + df
+        assert_frame_equal(result, expected)
+        result = df + 1
+        assert_frame_equal(result, expected)
+
+    @pytest.mark.parametrize('dtype', [None, object])
+    def test_frame_with_dtype_radd_nan(self, dtype):
+        df = pd.DataFrame([1, 2, 3], dtype=dtype)
+        expected = pd.DataFrame([np.nan, np.nan, np.nan], dtype=dtype)
+        result = np.nan + df
+        assert_frame_equal(result, expected)
+        result = df + np.nan
+        assert_frame_equal(result, expected)
+
+    def test_frame_radd_str(self):
+        df = pd.DataFrame(['x', np.nan, 'x'])
+        assert_frame_equal('a' + df, pd.DataFrame(['ax', np.nan, 'ax']))
+        assert_frame_equal(df + 'a', pd.DataFrame(['xa', np.nan, 'xa']))
+
+
 class TestDataFrameOperators(TestData):
 
     def test_operators(self):