fix for pandas-dev#16889 along with test

Author: hugo

pandas/core/indexing.py

@@ -760,10 +760,12 @@ def _align_frame(self, indexer, df):
             for i, ix in enumerate(indexer):
                 ax = self.obj.axes[i]
                 if is_sequence(ix) or isinstance(ix, slice):
+                    if isinstance(ix, np.ndarray):
+                        ix = ix.ravel()
                     if idx is None:
-                        idx = ax[ix].ravel()
+                        idx = ax[ix]
                     elif cols is None:
-                        cols = ax[ix].ravel()
+                        cols = ax[ix]
                     else:
                         break
                 else:

pandas/tests/indexing/test_datetime.py

@@ -7,7 +7,14 @@
 
 
 class TestDatetimeIndex(object):
-
+    def test_setitem_with_datetime_tz(self):
+        mask = np.array([True, False, True, False])
+        idx = pd.date_range('20010101', periods=4, tz='UTC')
+        df = pd.DataFrame({'a' : np.arange(4)}, index=idx).astype('float64')
+        test = df.copy()
+        test.loc[mask, :] = df.loc[mask, :]
+        tm.assert_frame_equal(test, df)
+        
     def test_indexing_with_datetime_tz(self):
 
         # 8260