Issue #15424: Add a __sizeof__ implementation for array objects.

Patch by Ludwig Hähne.
diff --git a/Lib/test/test_array.py b/Lib/test/test_array.py
index acf5b8f..74dccbf 100755
--- a/Lib/test/test_array.py
+++ b/Lib/test/test_array.py
@@ -985,6 +985,19 @@
         upper = long(pow(2, a.itemsize * 8)) - 1L
         self.check_overflow(lower, upper)
 
+    @test_support.cpython_only
+    def test_sizeof_with_buffer(self):
+        a = array.array(self.typecode, self.example)
+        basesize = test_support.calcvobjsize('4P')
+        buffer_size = a.buffer_info()[1] * a.itemsize
+        test_support.check_sizeof(self, a, basesize + buffer_size)
+
+    @test_support.cpython_only
+    def test_sizeof_without_buffer(self):
+        a = array.array(self.typecode)
+        basesize = test_support.calcvobjsize('4P')
+        test_support.check_sizeof(self, a, basesize)
+
 
 class ByteTest(SignedNumberTest):
     typecode = 'b'