Put fromisocalendar in PY38 block

Author: MomIsBestFriend

pandas/_libs/tslibs/nattype.pyx

@@ -19,6 +19,8 @@ from pandas._libs.tslibs.util cimport (
     get_nat, is_integer_object, is_float_object, is_datetime64_object,
     is_timedelta64_object)
 
+import pandas.compat as compat
+
 # ----------------------------------------------------------------------
 # Constants
 nat_strings = {'NaT', 'nat', 'NAT', 'nan', 'NaN', 'NAN'}
@@ -426,9 +428,10 @@ class NaTType(_NaT):
     toordinal = _make_error_func('toordinal', datetime)
     tzname = _make_error_func('tzname', datetime)
     utcoffset = _make_error_func('utcoffset', datetime)
-    fromisocalendar = _make_error_func(
-            'fromisocalendar', datetime.fromisocalendar.__doc__
-    )
+
+    # "fromisocalendar" was introduced in 3.8
+    if compat.PY38:
+        fromisocalendar = _make_error_func('fromisocalendar', datetime)
 
     # ----------------------------------------------------------------------
     # The remaining methods have docstrings copy/pasted from the analogous

pandas/tests/scalar/test_nat.py

@@ -141,6 +141,10 @@ def test_round_nat(klass, method, freq):
     ],
 )
 def test_nat_methods_raise(method):
+    # "fromisocalendar" was introduced in 3.8
+    if method == "fromisocalendar" and not compat.PY38:
+        method.remove("fromisocalendar")
+
     # see gh-9513, gh-17329
     msg = f"NaTType does not support {method}"
 
@@ -299,6 +303,10 @@ def test_overlap_public_nat_methods(klass, expected):
     if klass is Timestamp and not compat.PY37:
         expected.remove("fromisoformat")
 
+    # "fromisocalendar" was introduced in 3.8
+    if klass is Timestamp and not compat.PY38:
+        expected.remove("fromisocalendar")
+
     assert _get_overlap_public_nat_methods(klass) == expected