WIP, MAINT: upstream timedelta64 changes

* draft changes to allow pandas test
suite to pass with upstream NumPy
prohibition on integer -> m8 casting

Author: tylerjereddy

pandas/_libs/tslibs/timedeltas.pyx

@@ -1181,7 +1181,7 @@ class Timedelta(_Timedelta):
 
             kwargs = {key: _to_py_int_float(kwargs[key]) for key in kwargs}
 
-            nano = kwargs.pop('nanoseconds', 0)
+            nano = np.timedelta64(kwargs.pop('nanoseconds', 0))
             try:
                 value = nano + convert_to_timedelta64(timedelta(**kwargs),
                                                       'ns')

pandas/tests/arithmetic/test_datetime64.py

@@ -2137,7 +2137,12 @@ def test_timedelta64_equal_timedelta_supported_ops(self, op):
         #                   'us': 1}
 
         def timedelta64(*args):
-            return sum(starmap(np.timedelta64, zip(args, intervals)))
+            # integer types -> m8 casting will soon be prohibited
+            # in NumPy; avoid built-in sum() here to skip the casting
+            # prohibition in ufunc
+            # NOTE: extra list() call also added after switching from
+            # sum -> np.sum() to expand starmap object for later in test
+            return np.sum(list(starmap(np.timedelta64, zip(args, intervals))))
 
         for d, h, m, s, us in product(*([range(2)] * 5)):
             nptd = timedelta64(d, h, m, s, us)